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PostgreSQL: Declaring Variables

This PostgreSQL tutorial explains how to declare variables in PostgreSQL with syntax and examples.

What is a variable in PostgreSQL?

In PostgreSQL, a variable allows a programmer to store data temporarily during the execution of code.

The syntax to declare a variable in PostgreSQL is:

Parameters or Arguments

Example - declaring a variable.

Below is an example of how to declare a variable in PostgreSQL called vSite .

This example would declare a variable called vSite as a varchar data type.

You can then later set or change the value of the vSite variable, as follows:

This statement would set the vSite variable to a value of 'TechOnTheNet.com'.

Example - Declaring a variable with an initial value (not a constant)

Below is an example of how to declare a variable in PostgreSQL and give it an initial value. This is different from a constant in that the variable's value can be changed later.

This would declare a variable called vSite as a varchar data type and assign an initial value of 'TechOnTheNet.com'.

You could later change the value of the vSite variable, as follows:

This SET statement would change the vSite variable from a value of 'TechOnTheNet.com' to a value of 'CheckYourMath.com'.

Example - Declaring a constant

Below is an example of how to declare a constant in PostgreSQL called vSiteID .

This would declare a constant called vSiteID as an integer data type and assign an initial value of 50. Because this variable is declared using the CONSTANT keyword, you can not change its value after initializing the variable.

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How to Use Variables in PostgreSQL
PostgreSQL Howtos

Use DECLARE to Declare Variables in PostgreSQL

Use returning to assign value to variables in postgresql.

This article will demonstrate how we can declare and assign values to variables in PostgreSQL.

Usually, you’ll need variables in PL/SQL script. In the section called DECLARE , you need to tell the script what your variable is and what was its type.

In PL/SQL, there are two parts. One is the declaration, and another is the script part, where standard SQL is written. The format is like the following.

Now, we have a table of students and their tasks. Our job is to find a student that matches some condition and raise notice for the student.

The table Students is like the following:

Suppose you want to store the student name and task information, where id equals 3 . Now, here’s a thing to mention, we don’t know the data type of the id, name, and task.

If the type is a mismatch, then an error might occur. To resolve this, we need to use <column_name>%type .

If you’re running this sort of PL/SQL for the first time, RAISE will not work, meaning nothing will be shown after the execution of the SQL script. To enable this, you need to perform the following command in your psql shell.

After setting this, you can see the output like this (after executing the PL/SQL command):

Here’s another keyword, INTO . It places the data of your selected columns to the respective variables.

You’ve seen that the ID is the SERIAL type data from the above table. So, it will increase by one after every insertion.

But during the insertion, we never know which id is being assigned to the current row.

So, let’s say you want to see the ID after the insert command to the student table. The command will be as follows:

Also, you can use multiple queries inside the PL/SQL begin to part. Then, you can use the variable to check some conditions and do some CRUD operations.

More information is available here in the official documentation.

I'm Shihab Sikder, a professional Backend Developer with experience in problem-solving and content writing. Building secure, scalable, and reliable backend architecture is my motive. I'm working with two companies as a part-time backend engineer.

How to declare variables in PL/pgSQL stored procedures

Rajkumar Raghuwanshi

SUMMARY: This article covers how stored procedures can make use of variables to be more functional and useful. After defining PL/pgSQL, stored procedures, and variables, it provides examples of how variables can be used.

The title of this post makes use of 3 terms: PL/pgSQL, stored procedure, and variable. Let’s start with a basic understanding of them.

PL/pgSQL : An abbreviation for Procedure Language/PostgreSQL. It is a procedural language that provides the ability to perform more complex operations and computations than SQL.

Stored Procedure: A block for SQL statements combined together under a name and saved in database which can be called on multiple times when needed.

Variable: A variable holds a value that can be changed through the block. It is always associated with a datatype.

Now let’s try to understand these with examples.

Stored procedures include functions, procedures, triggers, and other objects that can be saved in databases. Below is a simple example for a stored procedure “Procedure”:

In this example, an SQL statement, which upon call prints “Procedure example1 called,” is saved under the name example1 and can be called multiple times as needed.

The example has a fixed message which it prints upon call. To make the function more dynamic and useful, we can use different types of variables and assign values to them at compile time as well at run time.

A variable must be declared in the declaration section of the PL/pgSQL block. Declaration syntax for a variable is: “ variable_name data_type [:=value/constant/expression]; ”

Variable_name: This can be any meaningful name or whatever the user wants.

Data_type: PostgreSQL supports data types like integer, numeric, varchar, and text, or it can be a %TYPE or %ROWTYPE. Here is a list of PostgreSQL supported data types: https://www.postgresql.org/docs/current/datatype.html .

Variable Assignment: Any value as accepted by data type, constant, or expression can be assigned to the variable. This part is optional.

The user can print variable values by using RAISE NOTICE/EXCEPTION and “%” as a placeholder to be replaced by the variable value.

Let’s see an example for variable declaration and display:

The variable can also be of a column type or a row type of a table. These can be declared with data type as %TYPE and %ROWTYPE. Here is an example:

In this example the data type of the variable “eid_var” is declared by reference to the “eid” column’s data type in the “emp” table As output the user wants to return a complete row (all columns) of the “emp” table, so the variable “result” is declared as a reference to a whole row type of the “emp” table.

Another point to notice is that the “result” variable is assigned at runtime by using the result set of SELECT * INTO.

Another way to use %ROWTYPE in PostgreSQL variables is using RECORD as the data type of a variable. Below is the same example as above, but displaying “emp” table data using RECORD type.

In the same way, the user can use variables in other stored procedures like function and triggers.

Reference Links:

https://www.postgresql.org/docs/current/datatype.html

https://www.postgresql.org/docs/current/plpgsql-declarations.html

https://www.postgresql.org/docs/current/sql-createprocedure.html

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PostgreSQL – Variables

In PostgreSQL , a variable is a meaningful name for a memory location that holds a value that can be changed throughout a block or function. A variable is always associated with a particular data type. Before using a variable, you must declare it in the declaration section of a PostgreSQL Block .

Let us better understand the Variables in PostgreSQL to better understand the concept.

The following illustrates the syntax for declaring a variable:

Let’s analyze the above syntax:

Variable Name : Specify the name of the variable. It is a good practice to assign a meaningful name to a variable. For example, instead of naming a variable “i” one should use index or counter .
Data Type : Associate a specific data type with the variable. The data type can be any valid PostgreSQL data type such as INTEGER , NUMERIC , VARCHAR , and CHAR .
Default Value : Optionally assign a default value to a variable. If you don’t, the initial value of the variable is initialized to NULL .

PostgreSQL Variables Examples

Let us take a look at some of the examples of Variables in PostgreSQL to better understand the concept.

Example 1: Basic Variable Declaration and Usage

Explanation: In this example, we declared four variables: ‘ counter' , ‘ first_name' , ‘ last_name' , and ‘ payment' . Each variable is initialized with a specific value. The ‘ RAISE NOTICE' statement is used to display the values of these variables.

Example 2: Using System Functions with Variables

Explanation: In this example, we declared a variable ‘ created_at' and initialized it with the current time using the NOW () function . The ‘ pg_sleep(10)' function pauses the execution for 10 seconds. The ‘ RAISE NOTICE' statements display the value of ‘ created_at' before and after the pause, showing that the time remains the same as it was initialized once.

Important Points About PostgreSQL Variables

Variables declared within a block or function are only accessible within that block or function. Variables can be assigned values using the := operator. Alternatively, you can use the SELECT INTO statement to assign values from queries to variables. When assigning values to variables, ensure that the data types are compatible. PostgreSQL will raise an error if there is a type mismatch. If a variable is not explicitly initialized, its default value is NULL .

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How to use a postgres variable in the select clause

With MSSQL it's easy, the @ marking the start of all variable names allows the parser to know that it is a variable not a column.

This is useful for things like injecting constant values where a select is providing the input to an insert table when copying from a staging table.

How do you express this for postgres?

2 Answers 2

PostgreSQL isn't as flexible in where and how it allows usage of variables. The closest thing for what you're trying to accomplish likely would be surrounding it in a DO block like so:

Note this is context dependent, and you can find more information in this StackOverflow answer .

Additionally you can create a function that declares variables and returns a value like so:

More information on this approach here .

2 This doesn't work, an anonymous DO block cannot return anything. – user1822 Commented Jan 15, 2021 at 6:53
@a_horse_with_no_name I'm not a PostgreSQL expert so I could be wrong, but the answer I linked and referenced it from with 139 upvoted is also wrong? – J.D. Commented Jan 15, 2021 at 13:57
Well, that answer is wrong as well and I am surprised it got so many upvotes despite throwing the error mentioned in one of the comments: " ERROR: query has no destination for result data " – user1822 Commented Jan 15, 2021 at 14:10
@a_horse_with_no_name Interesting, thanks. I'll look for an alternative to correct my answer. – J.D. Commented Jan 15, 2021 at 14:19
1 Actually it does work for my intended use case. The select statement will be providing rows to an insert statement and in fact this answer leads directly to a useful outcome, so I'll accept it provided JD qualifies it with the extra info and mentions the use case. Also, I have since found that if I create a function around the code this can't return a value BS goes away. – Peter Wone Commented Jan 16, 2021 at 11:44

SQL has no support for variables, this is only possible in procedural languages (in Postgres that would e.g. be PL/pgSQL).

The way to to this in plain SQL is to use a CTE (which is also a cross platform solution and not tied to any SQL dialect):

like injecting constant values where a select is providing the input to an insert table when copying from a staging table.

Well you don't need a variable for that:

Does your second expression work if 'some value' is text? I think it just gets interpreted as a column, no? – MikeB2019x Commented Mar 8, 2022 at 21:58
'some value' is a text (string) value – user1822 Commented Mar 8, 2022 at 22:44
In case if you still want to use a variable instead of 'some value' (e.g. to re-use it in multiple queries), you can put it like this: select col1, col2, :'my_var' from mytable; - note the single quotes, otherwise it will fail if the value is not alphanumeric word. – RAM237 Commented Jul 11 at 13:22

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Home » PostgreSQL PL/pgSQL » PL/pgSQL Select Into

PL/pgSQL Select Into

Summary : in this tutorial, you will learn how to use the PL/pgSQL select into statement to select data from the database and assign it to a variable.

Introduction to PL/pgSQL Select Into statement

The select into statement allows you to select data from the database and assign it to a variable .

Here’s the basic syntax of the select into statement:

In this syntax,

First, specify one or more columns from which you want to retrieve data in the select clause.
Second, place one or more variables after the into keyword.
Third, provide the name of the table in the from clause.

The select into statement will assign the data returned by the select clause to the corresponding variables.

Besides selecting data from a table, you can use other clauses of the select statement such as join , group by, and having .

PL/pgSQL Select Into statement examples

Let’s take some examples of using the select into statement.

1) Basic select into statement example

The following example uses the select into statement to retrieve the number of actors from the actor table and assign it to the actor_count variable:

In this example:

First, declare a variable called actor_count that stores the number of actors from the actor table.
Second, assign the number of actors to the actor_count using the select into statement.
Third, display a message that shows the value of the actor_count variable using the raise notice statement.

2) Using the select into with multiple variables

The following example uses the select into statement to assign the first and last names of the actor id 1 to two variables:

How it works.

First, declare two variables v_first_name and v_last_name with the types varchar :

Second, retrieve the first_name and last_name of the actor id 1 from the actor table and assign them to the v_first_name and v_last_name variables:

Third, show the values of v_first_name and v_last_name variables:

Because we assign data retrieved from the first_name and last_name columns of the actor table, we can use the type-copying technique to declare the v_first_name and v_last_name variables:

Use the select into statement to select data from the database and assign it to a variable.

Storing Select Query Results in Variables in PostgreSQL

By squashlabs, Last Updated: October 30, 2023

Storing Select Query Results in Variables in PostgreSQL

Assigning Select Query Results to Variables

Saving select query results to variables, capturing select query results in variables, storing output of select query in variables, syntax for assigning select query results to variables, saving output of select query to variables, capturing output of select query in variables, assigning select results to variables in postgresql, syntax for saving select query output to variables in postgresql, storing select query results in variables: a how-to guide, assigning select query results to variables in postgresql, saving select query results to variables: step-by-step, capturing select query results in variables: a practical approach, assigning select results to variables in postgresql: best practices, storing select query results in variables: tips and tricks, capturing select query results in variables: common pitfalls, assigning select query results to variables: dos and don’ts, saving select query results to variables in postgresql: in-depth, capturing output of select query in variables: advanced techniques.

Table of Contents

In PostgreSQL, you can assign the results of a SELECT query to variables for further processing. This can be useful when you want to store specific values from a query result and use them later in your code.

To assign the results of a SELECT query to a variable, you can use the SELECT INTO statement. Here’s the syntax:

Let’s say we have a table called “employees” with columns “id” and “name”. We want to assign the name of an employee with a specific ID to a variable. Here’s an example:

In this example, we declare a variable called “employee_name” with the same data type as the “name” column in the “employees” table. We then use the SELECT INTO statement to assign the name of an employee with ID 1 to the “employee_name” variable. Finally, we use the RAISE NOTICE statement to display the value of the variable.

You can use this technique to assign any column value to a variable. Just make sure the data type of the variable matches the data type of the column.

Related Article: Tutorial: Using isNumeric Function in PostgreSQL

In addition to assigning the results of a SELECT query to variables, you can also save the entire result set into a variable for further processing. This can be useful when you want to perform multiple operations on the result set without executing the query multiple times.

To save the results of a SELECT query to a variable, you can use the SELECT INTO statement with the ARRAY type. Here’s the syntax:

Let’s say we have a table called “products” with a column called “price”. We want to save all the prices of products with a specific category into an array variable. Here’s an example:

In this example, we declare an array variable called “product_prices” of type numeric[]. We then use the SELECT INTO statement with the ARRAY type to save all the prices of products with the category ‘Electronics’ into the “product_prices” variable. Finally, we use the RAISE NOTICE statement to display the values stored in the variable.

You can use this technique to save any column values to an array variable. Just make sure the data type of the array variable matches the data type of the column.

Apart from assigning or saving the results of a SELECT query to variables, you can also capture the query output in variables using the FETCH statement. This can be useful when you want to fetch the query results row by row and perform operations on each row individually.

To capture the results of a SELECT query in variables, you can use the FETCH statement with the INTO clause. Here’s the syntax:

Let’s say we have a cursor called “employee_cursor” that fetches the employee IDs and names from the “employees” table. We want to capture the employee IDs and names in separate variables. Here’s an example:

In this example, we declare two variables, “employee_id” of type integer and “employee_name” of type text. We then open the “employee_cursor” cursor, which fetches the employee IDs and names from the “employees” table. Inside the loop, we use the FETCH statement to capture each row of the query result in the variables “employee_id” and “employee_name”. We then use the RAISE NOTICE statement to display the values of the variables. The loop continues until there are no more rows to fetch. Finally, we close the cursor.

You can use this technique to capture any column values in variables row by row. Just make sure the data types of the variables match the data types of the columns.

To store the output of a SELECT query in variables in PostgreSQL, you can use various techniques such as SELECT INTO, ARRAY, and FETCH. These techniques allow you to assign specific column values, save the entire result set, or capture the query output row by row into variables for further processing.

Let’s summarize the syntax for each technique:

– Assigning Select Query Results to Variables:

– Saving Select Query Results to Variables:

– Capturing Select Query Results in Variables:

Using these techniques, you can easily store the output of a SELECT query in variables and manipulate the data as needed. Whether you need to assign specific values, save the entire result set, or process the output row by row, PostgreSQL provides the necessary tools to handle these scenarios.

Related Article: Tutorial: PostgreSQL Array Literals

To assign the results of a SELECT query to variables in PostgreSQL, you can use the SELECT INTO statement. This statement allows you to retrieve specific column values from a query result and store them in variables.

Here’s the syntax for assigning select query results to variables:

Let’s break down the syntax:

– SELECT: This keyword is used to specify the columns to retrieve from the table. – column_name: This is the name of the column you want to assign to the variable. – INTO: This keyword is used to indicate that the query result should be assigned to a variable. – variable_name: This is the name of the variable you want to assign the query result to. – FROM: This keyword is used to specify the table from which to retrieve the data. – table_name: This is the name of the table from which you want to retrieve the data. – WHERE: This keyword is used to specify any conditions for filtering the data. – condition: This is the condition or criteria that the data must meet to be included in the result.

Here’s an example that demonstrates the syntax:

You can use this syntax to assign any column value to a variable. Just make sure the data type of the variable matches the data type of the column.

In PostgreSQL, you can save the output of a SELECT query to variables for further processing. This can be useful when you want to perform multiple operations on the result set without executing the query multiple times.

To save the output of a SELECT query to variables, you can use the SELECT INTO statement with the ARRAY type. This allows you to store the entire result set in a variable as an array.

Here’s the syntax for saving the output of a SELECT query to variables:

– SELECT: This keyword is used to specify the columns to retrieve from the table. – column_name: This is the name of the column you want to include in the array. – INTO: This keyword is used to indicate that the query result should be saved to a variable. – ARRAY: This is the keyword that specifies the data type of the variable as an array. – table_name: This is the name of the table from which you want to retrieve the data. – WHERE: This keyword is used to specify any conditions for filtering the data. – condition: This is the condition or criteria that the data must meet to be included in the result.

You can use this syntax to save any column values to an array variable. Just make sure the data type of the array variable matches the data type of the column.

In PostgreSQL, you can capture the output of a SELECT query in variables using the FETCH statement. This allows you to fetch the query results row by row and perform operations on each row individually.

To capture the output of a SELECT query in variables, you can use the FETCH statement with the INTO clause. This allows you to specify the variables in which you want to store the query result.

Here’s the syntax for capturing the output of a SELECT query in variables:

– FETCH: This keyword is used to retrieve rows from a cursor. – direction: This is an optional parameter that specifies the direction in which to fetch the rows. It can be NEXT, PRIOR, FIRST, LAST, ABSOLUTE n, or RELATIVE n. – FROM: This keyword is used to specify the cursor from which to fetch the rows. – cursor_name: This is the name of the cursor from which you want to fetch the rows. – INTO: This keyword is used to indicate that the fetched rows should be stored in variables. – variable_name1, variable_name2, …: These are the variables in which you want to store the fetched rows.

You can use this syntax to capture any column values in variables row by row. Just make sure the data types of the variables match the data types of the columns.

Related Article: How to Use the ISNULL Function in PostgreSQL

To assign the results of a SELECT query to variables, you can use the SELECT INTO statement. This statement allows you to retrieve specific column values from a query result and store them in variables.

Here’s the syntax for assigning select results to variables:

Here’s another example that demonstrates assigning multiple column values to variables:

In this example, we declare two variables, “employee_id” and “employee_name”, with the same data types as the corresponding columns in the “employees” table. We then use the SELECT INTO statement to assign the ID and name of an employee with ID 1 to the variables. Finally, we use the RAISE NOTICE statement to display the values of the variables.

You can use this syntax to assign multiple column values to multiple variables in a single query.

To save the output of a SELECT query to variables in PostgreSQL, you can use the SELECT INTO statement with the ARRAY type. This allows you to store the entire result set in a variable as an array.

Here’s the syntax for saving select query output to variables:

Here’s another example that demonstrates saving multiple column values to multiple variables:

In this example, we declare two array variables, “employee_ids” of type integer[] and “employee_names” of type text[]. We then use the SELECT INTO statement with the ARRAY type to save all the IDs and names of employees into the respective variables. Finally, we use the RAISE NOTICE statement to display the values stored in the variables.

You can use this syntax to save multiple column values to multiple variables in a single query.

In PostgreSQL, storing select query results in variables can be a useful technique for manipulating and processing data. Whether you need to assign specific column values, save the entire result set, or capture the query output row by row, PostgreSQL provides a variety of methods to accomplish these tasks. In this guide, we will explore different techniques for storing select query results in variables and provide step-by-step examples to illustrate their usage.

Related Article: Integrating PostgreSQL While Loop into Database Operations

Here’s an example that demonstrates how to assign the name of an employee with a specific ID to a variable:

You can use this technique to assign multiple column values to multiple variables in a single query.

Here’s an example that demonstrates how to save all the prices of products with a specific category into an array variable:

You can use this technique to save multiple column values to multiple variables in a single query.

Apart from assigning or saving the results of a SELECT query to variables, you can also capture the query output in variables using the FETCH statement. This allows you to fetch the query results row by row and perform operations on each row individually.

Here’s an example that demonstrates how to capture the employee IDs and names from the “employees” table in variables:

Related Article: Tutorial: Modulo Operator in PostgreSQL Databases

When assigning select results to variables in PostgreSQL, it’s important to follow best practices to ensure efficient and reliable code. Here are some best practices to consider:

1. Use the correct data types: Make sure the data types of the variables match the data types of the columns you are assigning or capturing. This helps prevent data conversion errors and ensures the variables can hold the values properly.

2. Use descriptive variable names: Choose meaningful names for your variables that accurately reflect their purpose. This improves code readability and makes it easier for other developers to understand your code.

3. Handle exceptions: When assigning or capturing select results in variables, be prepared to handle exceptions that may occur. Use try-catch blocks or error handling mechanisms to gracefully handle any errors that may arise during the process.

4. Limit the number of variables: Avoid declaring unnecessary variables. Only declare variables that are necessary for storing the select results. This helps keep your code clean and reduces the risk of confusion or errors.

5. Close cursors after use: If you are using cursors to capture select results in variables, make sure to close the cursor after you have finished processing the data. This helps release system resources and improves performance.

Storing select query results in variables in PostgreSQL can be a useful technique for manipulating and processing data. Here are some tips and tricks to help you effectively use this feature:

1. Use the correct data types: When declaring variables to store select query results, make sure the data types of the variables match the data types of the columns you are assigning or capturing. This helps prevent data conversion errors and ensures the variables can hold the values properly.

2. Consider performance implications: Storing select query results in variables can have performance implications, especially if you are dealing with large result sets. Be mindful of the amount of data you are storing in variables and consider whether it is necessary to store the entire result set or just specific values.

3. Use cursors for large result sets: If you are dealing with a large result set, consider using cursors to fetch the data row by row instead of storing the entire result set in variables. This can help improve performance and reduce memory usage.

4. Handle NULL values: When assigning select query results to variables, be aware that NULL values can be returned. Make sure to handle NULL values appropriately in your code to avoid any unexpected behavior.

5. Use descriptive variable names: Choose meaningful names for your variables that accurately reflect their purpose. This improves code readability and makes it easier for other developers to understand your code.

6. Consider using arrays: If you need to store multiple values from a select query, consider using arrays to store the values in a single variable. This can help simplify your code and make it more efficient.

7. Be mindful of scope: When declaring variables to store select query results, make sure to define their scope appropriately. Variables declared within a block or a function are only accessible within that block or function.

8. Test and debug your code: Always test your code thoroughly and make use of debugging tools to ensure that your variables are storing the correct values. This can help identify any issues or unexpected behavior early on.

When capturing select query results in variables in PostgreSQL, it’s important to be aware of common pitfalls that can lead to errors or unexpected behavior. Here are some common pitfalls to watch out for:

1. Forgetting to open the cursor: If you are using a cursor to capture select query results in variables, make sure to open the cursor before fetching data from it. Failure to open the cursor will result in an error.

2. Forgetting to close the cursor: After you have finished processing the data, make sure to close the cursor to release system resources. Failure to close the cursor can lead to resource leaks and performance issues.

3. Not checking for the end of the result set: When using a cursor to fetch data row by row, make sure to check for the end of the result set using the NOT FOUND condition. Failure to do so can result in an infinite loop or incorrect processing of data.

4. Incorrect variable data types: Ensure that the data types of the variables you are capturing the select query results in match the data types of the columns you are fetching. Failure to do so can result in data conversion errors or unexpected behavior.

5. Handling NULL values: When capturing select query results in variables, be aware that NULL values can be returned. Make sure to handle NULL values appropriately in your code to avoid any unexpected behavior.

6. Scope of variables: Make sure to define the scope of your variables appropriately. Variables declared within a block or a function are only accessible within that block or function.

7. Performance considerations: Be mindful of the performance implications of capturing select query results in variables, especially if you are dealing with large result sets. Consider whether it is necessary to store the entire result set or just specific values.

8. Testing and debugging: Always test your code thoroughly and make use of debugging tools to ensure that your variables are capturing the correct values. This can help identify any issues or unexpected behavior early on.

Related Article: Incorporating Queries within PostgreSQL Case Statements

When assigning select query results to variables in PostgreSQL, it’s important to follow best practices and avoid common pitfalls. Here are some dos and don’ts to keep in mind:

Dos: 1. Do use the correct data types: Make sure the data types of the variables match the data types of the columns you are assigning. This helps prevent data conversion errors and ensures the variables can hold the values properly.

2. Do use descriptive variable names: Choose meaningful names for your variables that accurately reflect their purpose. This improves code readability and makes it easier for other developers to understand your code.

3. Do handle exceptions: Be prepared to handle exceptions that may occur when assigning select query results to variables. Use try-catch blocks or error handling mechanisms to gracefully handle any errors that may arise during the process.

4. Do limit the number of variables: Avoid declaring unnecessary variables. Only declare variables that are necessary for storing the select results. This helps keep your code clean and reduces the risk of confusion or errors.

5. Do test your code: Always test your code thoroughly to ensure that your variables are storing the correct values. Use test cases that cover different scenarios and edge cases to validate the behavior of your code.

Don’ts: 1. Don’t forget to check for NULL values: When assigning select query results to variables, be aware that NULL values can be returned. Make sure to handle NULL values appropriately in your code to avoid any unexpected behavior.

2. Don’t use ambiguous variable names: Avoid using generic or ambiguous variable names that do not provide any meaningful information about the data they store. This can make your code harder to read and understand.

3. Don’t forget to close cursors: If you are using cursors to assign select query results to variables, make sure to close the cursor after you have finished processing the data. Failure to close the cursor can lead to resource leaks and performance issues.

4. Don’t ignore performance considerations: Be mindful of the performance implications of assigning select query results to variables, especially if you are dealing with large result sets. Consider whether it is necessary to store the entire result set or just specific values.

5. Don’t skip error handling: Always handle errors that may occur when assigning select query results to variables. Ignoring error handling can result in unexpected behavior and make it difficult to debug issues in your code.

When working with select query results in PostgreSQL, you may need to save them to variables for further processing. This can be useful when you want to perform multiple operations on the result set without executing the query multiple times. PostgreSQL provides several ways to save select query results to variables, giving you flexibility in how you handle and manipulate the data. In this section, we will explore these techniques in-depth and provide examples to illustrate their usage.

Using the SELECT INTO Statement

One way to save select query results to variables in PostgreSQL is to use the SELECT INTO statement. This statement allows you to assign specific column values from a query result to variables.

Here’s an example that demonstrates how to save the name of an employee with a specific ID to a variable:

You can use this technique to save any column value to a variable. Just make sure the data type of the variable matches the data type of the column.

Using the ARRAY Type

Another way to save select query results to variables in PostgreSQL is to use the ARRAY type. This allows you to save the entire result set as an array variable.

Using Cursors

Cursors provide another way to save select query results to variables in PostgreSQL. Cursors allow you to fetch the query output row by row and store the values in variables.

Here’s an example that demonstrates how to save the employee IDs and names from the “employees” table in variables using a cursor:

You can use this technique to save any column values to variables row by row. Just make sure the data types of the variables match the data types of the columns.

Capturing the output of a select query in variables in PostgreSQL opens up a world of possibilities for advanced data manipulation and processing. In addition to the basic techniques we have covered, there are several advanced techniques you can use to harness the full power of this feature. In this section, we will explore some of these techniques and provide examples to illustrate their usage.

Using Record Variables

Record variables in PostgreSQL allow you to capture the output of a select query that returns multiple columns into a single variable. This can be useful when you want to perform complex operations on the query result without the need to declare separate variables for each column.

Here’s an example that demonstrates how to capture the employee ID and name in a record variable:

In this example, we declare a record variable called “employee_record” of type “employees%ROWTYPE”. We then use the SELECT INTO statement to capture the output of the query that selects all columns from the “employees” table into the “employee_record” variable. Finally, we use the RAISE NOTICE statement to display the values of the individual columns within the record variable.

You can use this technique to capture the output of a select query with any number of columns into a record variable. Just make sure the record variable is defined with the same structure as the query result.

Using Composite Types

Composite types in PostgreSQL allow you to define custom data types that can be used to capture the output of select queries. This can be useful when you want to encapsulate related columns into a single variable and pass it around as a single unit.

Here’s an example that demonstrates how to define a composite type and capture the employee ID and name in a variable of that type:

In this example, we first create a composite type called “employee_info” that consists of an “id” column of type integer and a “name” column of type text. We then declare a variable called “employee_data” of type “employee_info”. We use the SELECT INTO statement to capture the employee ID and name from the “employees” table into the “employee_data” variable. Finally, we use the RAISE NOTICE statement to display the values of the individual fields within the composite variable.

You can use this technique to define custom composite types for capturing the output of select queries with any number of columns. Just make sure the composite variable is defined with the same structure as the query result.

Using Arrays of Composite Types

Building on the previous technique, you can also use arrays of composite types to capture the output of select queries that return multiple rows. This can be useful when you want to store a collection of related rows in a single variable.

Here’s an example that demonstrates how to define an array of a composite type and capture the employee ID and name for multiple employees:

In this example, we first create a composite type called “employee_info” that consists of an “id” column of type integer and a “name” column of type text. We then declare a variable called “employee_data” of type “employee_info[]”, which is an array of the composite type. We use the SELECT INTO statement with the ARRAY type to capture the employee ID and name for all employees from the “employees” table into the “employee_data” variable. Finally, we use a loop to iterate over the elements of the array and use the RAISE NOTICE statement to display the values of the individual fields within each composite variable.

You can use this technique to capture the output of select queries that return multiple rows into arrays of composite types. Just make sure the composite type and the array variable are defined with the same structure as the query result.

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psql
		PostgreSQL Client Applications

psql — PostgreSQL interactive terminal

psql [ option ...] [ dbname [ username ]]

Description

psql is a terminal-based front-end to PostgreSQL . It enables you to type in queries interactively, issue them to PostgreSQL , and see the query results. Alternatively, input can be from a file or from command line arguments. In addition, psql provides a number of meta-commands and various shell-like features to facilitate writing scripts and automating a wide variety of tasks.

Print all nonempty input lines to standard output as they are read. (This does not apply to lines read interactively.) This is equivalent to setting the variable ECHO to all .

Switches to unaligned output mode. (The default output mode is aligned .) This is equivalent to \pset format unaligned .

Print failed SQL commands to standard error output. This is equivalent to setting the variable ECHO to errors .

Specifies that psql is to execute the given command string, command . This option can be repeated and combined in any order with the -f option. When either -c or -f is specified, psql does not read commands from standard input; instead it terminates after processing all the -c and -f options in sequence.

command must be either a command string that is completely parsable by the server (i.e., it contains no psql -specific features), or a single backslash command. Thus you cannot mix SQL and psql meta-commands within a -c option. To achieve that, you could use repeated -c options or pipe the string into psql , for example:

( \\ is the separator meta-command.)

Each SQL command string passed to -c is sent to the server as a single request. Because of this, the server executes it as a single transaction even if the string contains multiple SQL commands, unless there are explicit BEGIN / COMMIT commands included in the string to divide it into multiple transactions. (See Section 55.2.2.1 for more details about how the server handles multi-query strings.)

If having several commands executed in one transaction is not desired, use repeated -c commands or feed multiple commands to psql 's standard input, either using echo as illustrated above, or via a shell here-document, for example:

Switches to CSV (Comma-Separated Values) output mode. This is equivalent to \pset format csv .

Specifies the name of the database to connect to. This is equivalent to specifying dbname as the first non-option argument on the command line. The dbname can be a connection string . If so, connection string parameters will override any conflicting command line options.

Copy all SQL commands sent to the server to standard output as well. This is equivalent to setting the variable ECHO to queries .

Echo the actual queries generated by \d and other backslash commands. You can use this to study psql 's internal operations. This is equivalent to setting the variable ECHO_HIDDEN to on .

Read commands from the file filename , rather than standard input. This option can be repeated and combined in any order with the -c option. When either -c or -f is specified, psql does not read commands from standard input; instead it terminates after processing all the -c and -f options in sequence. Except for that, this option is largely equivalent to the meta-command \i .

If filename is - (hyphen), then standard input is read until an EOF indication or \q meta-command. This can be used to intersperse interactive input with input from files. Note however that Readline is not used in this case (much as if -n had been specified).

Using this option is subtly different from writing psql < filename . In general, both will do what you expect, but using -f enables some nice features such as error messages with line numbers. There is also a slight chance that using this option will reduce the start-up overhead. On the other hand, the variant using the shell's input redirection is (in theory) guaranteed to yield exactly the same output you would have received had you entered everything by hand.

Use separator as the field separator for unaligned output. This is equivalent to \pset fieldsep or \f .

Specifies the host name of the machine on which the server is running. If the value begins with a slash, it is used as the directory for the Unix-domain socket.

Switches to HTML output mode. This is equivalent to \pset format html or the \H command.

List all available databases, then exit. Other non-connection options are ignored. This is similar to the meta-command \list .

When this option is used, psql will connect to the database postgres , unless a different database is named on the command line (option -d or non-option argument, possibly via a service entry, but not via an environment variable).

Write all query output into file filename , in addition to the normal output destination.

Do not use Readline for line editing and do not use the command history (see the section called “Command-Line Editing” below).

Put all query output into file filename . This is equivalent to the command \o .

Specifies the TCP port or the local Unix-domain socket file extension on which the server is listening for connections. Defaults to the value of the PGPORT environment variable or, if not set, to the port specified at compile time, usually 5432.

Specifies printing options, in the style of \pset . Note that here you have to separate name and value with an equal sign instead of a space. For example, to set the output format to LaTeX , you could write -P format=latex .

Specifies that psql should do its work quietly. By default, it prints welcome messages and various informational output. If this option is used, none of this happens. This is useful with the -c option. This is equivalent to setting the variable QUIET to on .

Use separator as the record separator for unaligned output. This is equivalent to \pset recordsep .

Run in single-step mode. That means the user is prompted before each command is sent to the server, with the option to cancel execution as well. Use this to debug scripts.

Runs in single-line mode where a newline terminates an SQL command, as a semicolon does.

This mode is provided for those who insist on it, but you are not necessarily encouraged to use it. In particular, if you mix SQL and meta-commands on a line the order of execution might not always be clear to the inexperienced user.

Turn off printing of column names and result row count footers, etc. This is equivalent to \t or \pset tuples_only .

Specifies options to be placed within the HTML table tag. See \pset tableattr for details.

Connect to the database as the user username instead of the default. (You must have permission to do so, of course.)

Perform a variable assignment, like the \set meta-command. Note that you must separate name and value, if any, by an equal sign on the command line. To unset a variable, leave off the equal sign. To set a variable with an empty value, use the equal sign but leave off the value. These assignments are done during command line processing, so variables that reflect connection state will get overwritten later.

Print the psql version and exit.

Never issue a password prompt. If the server requires password authentication and a password is not available from other sources such as a .pgpass file, the connection attempt will fail. This option can be useful in batch jobs and scripts where no user is present to enter a password.

Note that this option will remain set for the entire session, and so it affects uses of the meta-command \connect as well as the initial connection attempt.

Force psql to prompt for a password before connecting to a database, even if the password will not be used.

If the server requires password authentication and a password is not available from other sources such as a .pgpass file, psql will prompt for a password in any case. However, psql will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.

Turn on the expanded table formatting mode. This is equivalent to \x or \pset expanded .

Do not read the start-up file (neither the system-wide psqlrc file nor the user's ~/.psqlrc file).

Set the field separator for unaligned output to a zero byte. This is equivalent to \pset fieldsep_zero .

Set the record separator for unaligned output to a zero byte. This is useful for interfacing, for example, with xargs -0 . This is equivalent to \pset recordsep_zero .

This option can only be used in combination with one or more -c and/or -f options. It causes psql to issue a BEGIN command before the first such option and a COMMIT command after the last one, thereby wrapping all the commands into a single transaction. If any of the commands fails and the variable ON_ERROR_STOP was set, a ROLLBACK command is sent instead. This ensures that either all the commands complete successfully, or no changes are applied.

If the commands themselves contain BEGIN , COMMIT , or ROLLBACK , this option will not have the desired effects. Also, if an individual command cannot be executed inside a transaction block, specifying this option will cause the whole transaction to fail.

Show help about psql and exit. The optional topic parameter (defaulting to options ) selects which part of psql is explained: commands describes psql 's backslash commands; options describes the command-line options that can be passed to psql ; and variables shows help about psql configuration variables.

Exit Status

psql returns 0 to the shell if it finished normally, 1 if a fatal error of its own occurs (e.g., out of memory, file not found), 2 if the connection to the server went bad and the session was not interactive, and 3 if an error occurred in a script and the variable ON_ERROR_STOP was set.

Connecting to a Database

psql is a regular PostgreSQL client application. In order to connect to a database you need to know the name of your target database, the host name and port number of the server, and what database user name you want to connect as. psql can be told about those parameters via command line options, namely -d , -h , -p , and -U respectively. If an argument is found that does not belong to any option it will be interpreted as the database name (or the database user name, if the database name is already given). Not all of these options are required; there are useful defaults. If you omit the host name, psql will connect via a Unix-domain socket to a server on the local host, or via TCP/IP to localhost on Windows. The default port number is determined at compile time. Since the database server uses the same default, you will not have to specify the port in most cases. The default database user name is your operating-system user name. Once the database user name is determined, it is used as the default database name. Note that you cannot just connect to any database under any database user name. Your database administrator should have informed you about your access rights.

When the defaults aren't quite right, you can save yourself some typing by setting the environment variables PGDATABASE , PGHOST , PGPORT and/or PGUSER to appropriate values. (For additional environment variables, see Section 34.15 .) It is also convenient to have a ~/.pgpass file to avoid regularly having to type in passwords. See Section 34.16 for more information.

An alternative way to specify connection parameters is in a conninfo string or a URI , which is used instead of a database name. This mechanism give you very wide control over the connection. For example:

This way you can also use LDAP for connection parameter lookup as described in Section 34.18 . See Section 34.1.2 for more information on all the available connection options.

If the connection could not be made for any reason (e.g., insufficient privileges, server is not running on the targeted host, etc.), psql will return an error and terminate.

If both standard input and standard output are a terminal, then psql sets the client encoding to “ auto ” , which will detect the appropriate client encoding from the locale settings ( LC_CTYPE environment variable on Unix systems). If this doesn't work out as expected, the client encoding can be overridden using the environment variable PGCLIENTENCODING .

Entering SQL Commands

In normal operation, psql provides a prompt with the name of the database to which psql is currently connected, followed by the string => . For example:

At the prompt, the user can type in SQL commands. Ordinarily, input lines are sent to the server when a command-terminating semicolon is reached. An end of line does not terminate a command. Thus commands can be spread over several lines for clarity. If the command was sent and executed without error, the results of the command are displayed on the screen.

If untrusted users have access to a database that has not adopted a secure schema usage pattern , begin your session by removing publicly-writable schemas from search_path . One can add options=-csearch_path= to the connection string or issue SELECT pg_catalog.set_config('search_path', '', false) before other SQL commands. This consideration is not specific to psql ; it applies to every interface for executing arbitrary SQL commands.

Whenever a command is executed, psql also polls for asynchronous notification events generated by LISTEN and NOTIFY .

While C-style block comments are passed to the server for processing and removal, SQL-standard comments are removed by psql .

Meta-Commands

Anything you enter in psql that begins with an unquoted backslash is a psql meta-command that is processed by psql itself. These commands make psql more useful for administration or scripting. Meta-commands are often called slash or backslash commands.

The format of a psql command is the backslash, followed immediately by a command verb, then any arguments. The arguments are separated from the command verb and each other by any number of whitespace characters.

To include whitespace in an argument you can quote it with single quotes. To include a single quote in an argument, write two single quotes within single-quoted text. Anything contained in single quotes is furthermore subject to C-like substitutions for \n (new line), \t (tab), \b (backspace), \r (carriage return), \f (form feed), \ digits (octal), and \x digits (hexadecimal). A backslash preceding any other character within single-quoted text quotes that single character, whatever it is.

If an unquoted colon ( : ) followed by a psql variable name appears within an argument, it is replaced by the variable's value, as described in SQL Interpolation below. The forms :' variable_name ' and :" variable_name " described there work as well. The :{? variable_name } syntax allows testing whether a variable is defined. It is substituted by TRUE or FALSE. Escaping the colon with a backslash protects it from substitution.

Within an argument, text that is enclosed in backquotes ( ` ) is taken as a command line that is passed to the shell. The output of the command (with any trailing newline removed) replaces the backquoted text. Within the text enclosed in backquotes, no special quoting or other processing occurs, except that appearances of : variable_name where variable_name is a psql variable name are replaced by the variable's value. Also, appearances of :' variable_name ' are replaced by the variable's value suitably quoted to become a single shell command argument. (The latter form is almost always preferable, unless you are very sure of what is in the variable.) Because carriage return and line feed characters cannot be safely quoted on all platforms, the :' variable_name ' form prints an error message and does not substitute the variable value when such characters appear in the value.

Some commands take an SQL identifier (such as a table name) as argument. These arguments follow the syntax rules of SQL : Unquoted letters are forced to lowercase, while double quotes ( " ) protect letters from case conversion and allow incorporation of whitespace into the identifier. Within double quotes, paired double quotes reduce to a single double quote in the resulting name. For example, FOO"BAR"BAZ is interpreted as fooBARbaz , and "A weird"" name" becomes A weird" name .

Parsing for arguments stops at the end of the line, or when another unquoted backslash is found. An unquoted backslash is taken as the beginning of a new meta-command. The special sequence \\ (two backslashes) marks the end of arguments and continues parsing SQL commands, if any. That way SQL and psql commands can be freely mixed on a line. But in any case, the arguments of a meta-command cannot continue beyond the end of the line.

Many of the meta-commands act on the current query buffer . This is simply a buffer holding whatever SQL command text has been typed but not yet sent to the server for execution. This will include previous input lines as well as any text appearing before the meta-command on the same line.

The following meta-commands are defined:

If the current table output format is unaligned, it is switched to aligned. If it is not unaligned, it is set to unaligned. This command is kept for backwards compatibility. See \pset for a more general solution.

Sets query parameters for the next query execution, with the specified parameters passed for any parameter placeholders ( $1 etc.).

This also works for query-execution commands besides \g , such as \gx and \gset .

This command causes the extended query protocol (see Section 55.1.2 ) to be used, unlike normal psql operation, which uses the simple query protocol. So this command can be useful to test the extended query protocol from psql. (The extended query protocol is used even if the query has no parameters and this command specifies zero parameters.) This command affects only the next query executed; all subsequent queries will use the simple query protocol by default.

Establishes a new connection to a PostgreSQL server. The connection parameters to use can be specified either using a positional syntax (one or more of database name, user, host, and port), or using a conninfo connection string as detailed in Section 34.1.1 . If no arguments are given, a new connection is made using the same parameters as before.

Specifying any of dbname , username , host or port as - is equivalent to omitting that parameter.

The new connection can re-use connection parameters from the previous connection; not only database name, user, host, and port, but other settings such as sslmode . By default, parameters are re-used in the positional syntax, but not when a conninfo string is given. Passing a first argument of -reuse-previous=on or -reuse-previous=off overrides that default. If parameters are re-used, then any parameter not explicitly specified as a positional parameter or in the conninfo string is taken from the existing connection's parameters. An exception is that if the host setting is changed from its previous value using the positional syntax, any hostaddr setting present in the existing connection's parameters is dropped. Also, any password used for the existing connection will be re-used only if the user, host, and port settings are not changed. When the command neither specifies nor reuses a particular parameter, the libpq default is used.

If the new connection is successfully made, the previous connection is closed. If the connection attempt fails (wrong user name, access denied, etc.), the previous connection will be kept if psql is in interactive mode. But when executing a non-interactive script, the old connection is closed and an error is reported. That may or may not terminate the script; if it does not, all database-accessing commands will fail until another \connect command is successfully executed. This distinction was chosen as a user convenience against typos on the one hand, and a safety mechanism that scripts are not accidentally acting on the wrong database on the other hand. Note that whenever a \connect command attempts to re-use parameters, the values re-used are those of the last successful connection, not of any failed attempts made subsequently. However, in the case of a non-interactive \connect failure, no parameters are allowed to be re-used later, since the script would likely be expecting the values from the failed \connect to be re-used.

Sets the title of any tables being printed as the result of a query or unset any such title. This command is equivalent to \pset title title . (The name of this command derives from “ caption ” , as it was previously only used to set the caption in an HTML table.)

Changes the current working directory to directory . Without argument, changes to the current user's home directory.

To print your current working directory, use \! pwd .

Outputs information about the current database connection.

Performs a frontend (client) copy. This is an operation that runs an SQL COPY command, but instead of the server reading or writing the specified file, psql reads or writes the file and routes the data between the server and the local file system. This means that file accessibility and privileges are those of the local user, not the server, and no SQL superuser privileges are required.

When program is specified, command is executed by psql and the data passed from or to command is routed between the server and the client. Again, the execution privileges are those of the local user, not the server, and no SQL superuser privileges are required.

For \copy ... from stdin , data rows are read from the same source that issued the command, continuing until \. is read or the stream reaches EOF . This option is useful for populating tables in-line within an SQL script file. For \copy ... to stdout , output is sent to the same place as psql command output, and the COPY count command status is not printed (since it might be confused with a data row). To read/write psql 's standard input or output regardless of the current command source or \o option, write from pstdin or to pstdout .

The syntax of this command is similar to that of the SQL COPY command. All options other than the data source/destination are as specified for COPY . Because of this, special parsing rules apply to the \copy meta-command. Unlike most other meta-commands, the entire remainder of the line is always taken to be the arguments of \copy , and neither variable interpolation nor backquote expansion are performed in the arguments.

Another way to obtain the same result as \copy ... to is to use the SQL COPY ... TO STDOUT command and terminate it with \g filename or \g | program . Unlike \copy , this method allows the command to span multiple lines; also, variable interpolation and backquote expansion can be used.

These operations are not as efficient as the SQL COPY command with a file or program data source or destination, because all data must pass through the client/server connection. For large amounts of data the SQL command might be preferable. Also, because of this pass-through method, \copy ... from in CSV mode will erroneously treat a \. data value alone on a line as an end-of-input marker.

Shows the copyright and distribution terms of PostgreSQL .

Executes the current query buffer (like \g ) and shows the results in a crosstab grid. The query must return at least three columns. The output column identified by colV becomes a vertical header and the output column identified by colH becomes a horizontal header. colD identifies the output column to display within the grid. sortcolH identifies an optional sort column for the horizontal header.

Each column specification can be a column number (starting at 1) or a column name. The usual SQL case folding and quoting rules apply to column names. If omitted, colV is taken as column 1 and colH as column 2. colH must differ from colV . If colD is not specified, then there must be exactly three columns in the query result, and the column that is neither colV nor colH is taken to be colD .

The vertical header, displayed as the leftmost column, contains the values found in column colV , in the same order as in the query results, but with duplicates removed.

The horizontal header, displayed as the first row, contains the values found in column colH , with duplicates removed. By default, these appear in the same order as in the query results. But if the optional sortcolH argument is given, it identifies a column whose values must be integer numbers, and the values from colH will appear in the horizontal header sorted according to the corresponding sortcolH values.

Inside the crosstab grid, for each distinct value x of colH and each distinct value y of colV , the cell located at the intersection (x,y) contains the value of the colD column in the query result row for which the value of colH is x and the value of colV is y . If there is no such row, the cell is empty. If there are multiple such rows, an error is reported.

For each relation (table, view, materialized view, index, sequence, or foreign table) or composite type matching the pattern , show all columns, their types, the tablespace (if not the default) and any special attributes such as NOT NULL or defaults. Associated indexes, constraints, rules, and triggers are also shown. For foreign tables, the associated foreign server is shown as well. ( “ Matching the pattern ” is defined in Patterns below.)

For some types of relation, \d shows additional information for each column: column values for sequences, indexed expressions for indexes, and foreign data wrapper options for foreign tables.

The command form \d+ is identical, except that more information is displayed: any comments associated with the columns of the table are shown, as is the presence of OIDs in the table, the view definition if the relation is a view, a non-default replica identity setting and the access method name if the relation has an access method.

By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects.

If \d is used without a pattern argument, it is equivalent to \dtvmsE which will show a list of all visible tables, views, materialized views, sequences and foreign tables. This is purely a convenience measure.

Lists aggregate functions, together with their return type and the data types they operate on. If pattern is specified, only aggregates whose names match the pattern are shown. By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects.

Lists access methods. If pattern is specified, only access methods whose names match the pattern are shown. If + is appended to the command name, each access method is listed with its associated handler function and description.

Lists operator classes (see Section 38.16.1 ). If access-method-pattern is specified, only operator classes associated with access methods whose names match that pattern are listed. If input-type-pattern is specified, only operator classes associated with input types whose names match that pattern are listed. If + is appended to the command name, each operator class is listed with its associated operator family and owner.

Lists operator families (see Section 38.16.5 ). If access-method-pattern is specified, only operator families associated with access methods whose names match that pattern are listed. If input-type-pattern is specified, only operator families associated with input types whose names match that pattern are listed. If + is appended to the command name, each operator family is listed with its owner.

Lists operators associated with operator families (see Section 38.16.2 ). If access-method-pattern is specified, only members of operator families associated with access methods whose names match that pattern are listed. If operator-family-pattern is specified, only members of operator families whose names match that pattern are listed. If + is appended to the command name, each operator is listed with its sort operator family (if it is an ordering operator).

Lists support functions associated with operator families (see Section 38.16.3 ). If access-method-pattern is specified, only functions of operator families associated with access methods whose names match that pattern are listed. If operator-family-pattern is specified, only functions of operator families whose names match that pattern are listed. If + is appended to the command name, functions are displayed verbosely, with their actual parameter lists.

Lists tablespaces. If pattern is specified, only tablespaces whose names match the pattern are shown. If + is appended to the command name, each tablespace is listed with its associated options, on-disk size, permissions and description.

Lists conversions between character-set encodings. If pattern is specified, only conversions whose names match the pattern are listed. By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects. If + is appended to the command name, each object is listed with its associated description.

Lists server configuration parameters and their values. If pattern is specified, only parameters whose names match the pattern are listed. Without a pattern , only parameters that are set to non-default values are listed. (Use \dconfig * to see all parameters.) If + is appended to the command name, each parameter is listed with its data type, context in which the parameter can be set, and access privileges (if non-default access privileges have been granted).

Lists type casts. If pattern is specified, only casts whose source or target types match the pattern are listed. If + is appended to the command name, each object is listed with its associated description.

Shows the descriptions of objects of type constraint , operator class , operator family , rule , and trigger . All other comments may be viewed by the respective backslash commands for those object types.

\dd displays descriptions for objects matching the pattern , or of visible objects of the appropriate type if no argument is given. But in either case, only objects that have a description are listed. By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects.

Descriptions for objects can be created with the COMMENT SQL command.

Lists domains. If pattern is specified, only domains whose names match the pattern are shown. By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects. If + is appended to the command name, each object is listed with its associated permissions and description.

Lists default access privilege settings. An entry is shown for each role (and schema, if applicable) for which the default privilege settings have been changed from the built-in defaults. If pattern is specified, only entries whose role name or schema name matches the pattern are listed.

The ALTER DEFAULT PRIVILEGES command is used to set default access privileges. The meaning of the privilege display is explained in Section 5.7 .

In this group of commands, the letters E , i , m , s , t , and v stand for foreign table, index, materialized view, sequence, table, and view, respectively. You can specify any or all of these letters, in any order, to obtain a listing of objects of these types. For example, \dti lists tables and indexes. If + is appended to the command name, each object is listed with its persistence status (permanent, temporary, or unlogged), physical size on disk, and associated description if any. If pattern is specified, only objects whose names match the pattern are listed. By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects.

Lists foreign servers (mnemonic: “ external servers ” ). If pattern is specified, only those servers whose name matches the pattern are listed. If the form \des+ is used, a full description of each server is shown, including the server's access privileges, type, version, options, and description.

Lists foreign tables (mnemonic: “ external tables ” ). If pattern is specified, only entries whose table name or schema name matches the pattern are listed. If the form \det+ is used, generic options and the foreign table description are also displayed.

Lists user mappings (mnemonic: “ external users ” ). If pattern is specified, only those mappings whose user names match the pattern are listed. If the form \deu+ is used, additional information about each mapping is shown.

\deu+ might also display the user name and password of the remote user, so care should be taken not to disclose them.

Lists foreign-data wrappers (mnemonic: “ external wrappers ” ). If pattern is specified, only those foreign-data wrappers whose name matches the pattern are listed. If the form \dew+ is used, the access privileges, options, and description of the foreign-data wrapper are also shown.

Lists functions, together with their result data types, argument data types, and function types, which are classified as “ agg ” (aggregate), “ normal ” , “ procedure ” , “ trigger ” , or “ window ” . To display only functions of specific type(s), add the corresponding letters a , n , p , t , or w to the command. If pattern is specified, only functions whose names match the pattern are shown. Any additional arguments are type-name patterns, which are matched to the type names of the first, second, and so on arguments of the function. (Matching functions can have more arguments than what you specify. To prevent that, write a dash - as the last arg_pattern .) By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects. If the form \df+ is used, additional information about each function is shown, including volatility, parallel safety, owner, security classification, access privileges, language, internal name (for C and internal functions only), and description. Source code for a specific function can be seen using \sf .

Lists text search configurations. If pattern is specified, only configurations whose names match the pattern are shown. If the form \dF+ is used, a full description of each configuration is shown, including the underlying text search parser and the dictionary list for each parser token type.

Lists text search dictionaries. If pattern is specified, only dictionaries whose names match the pattern are shown. If the form \dFd+ is used, additional information is shown about each selected dictionary, including the underlying text search template and the option values.

Lists text search parsers. If pattern is specified, only parsers whose names match the pattern are shown. If the form \dFp+ is used, a full description of each parser is shown, including the underlying functions and the list of recognized token types.

Lists text search templates. If pattern is specified, only templates whose names match the pattern are shown. If the form \dFt+ is used, additional information is shown about each template, including the underlying function names.

Lists database roles. (Since the concepts of “ users ” and “ groups ” have been unified into “ roles ” , this command is now equivalent to \du .) By default, only user-created roles are shown; supply the S modifier to include system roles. If pattern is specified, only those roles whose names match the pattern are listed. If the form \dg+ is used, additional information is shown about each role; currently this adds the comment for each role.

This is an alias for \lo_list , which shows a list of large objects. If + is appended to the command name, each large object is listed with its associated permissions, if any.

Lists procedural languages. If pattern is specified, only languages whose names match the pattern are listed. By default, only user-created languages are shown; supply the S modifier to include system objects. If + is appended to the command name, each language is listed with its call handler, validator, access privileges, and whether it is a system object.

Lists schemas (namespaces). If pattern is specified, only schemas whose names match the pattern are listed. By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects. If + is appended to the command name, each object is listed with its associated permissions and description, if any.

Lists operators with their operand and result types. If pattern is specified, only operators whose names match the pattern are listed. If one arg_pattern is specified, only prefix operators whose right argument's type name matches that pattern are listed. If two arg_pattern s are specified, only binary operators whose argument type names match those patterns are listed. (Alternatively, write - for the unused argument of a unary operator.) By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects. If + is appended to the command name, additional information about each operator is shown, currently just the name of the underlying function.

Lists collations. If pattern is specified, only collations whose names match the pattern are listed. By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects. If + is appended to the command name, each collation is listed with its associated description, if any. Note that only collations usable with the current database's encoding are shown, so the results may vary in different databases of the same installation.

Lists tables, views and sequences with their associated access privileges. If pattern is specified, only tables, views and sequences whose names match the pattern are listed. By default only user-created objects are shown; supply a pattern or the S modifier to include system objects.

The GRANT and REVOKE commands are used to set access privileges. The meaning of the privilege display is explained in Section 5.7 .

Lists partitioned relations. If pattern is specified, only entries whose name matches the pattern are listed. The modifiers t (tables) and i (indexes) can be appended to the command, filtering the kind of relations to list. By default, partitioned tables and indexes are listed.

If the modifier n ( “ nested ” ) is used, or a pattern is specified, then non-root partitioned relations are included, and a column is shown displaying the parent of each partitioned relation.

If + is appended to the command name, the sum of the sizes of each relation's partitions is also displayed, along with the relation's description. If n is combined with + , two sizes are shown: one including the total size of directly-attached leaf partitions, and another showing the total size of all partitions, including indirectly attached sub-partitions.

Lists defined configuration settings. These settings can be role-specific, database-specific, or both. role-pattern and database-pattern are used to select specific roles and databases to list, respectively. If omitted, or if * is specified, all settings are listed, including those not role-specific or database-specific, respectively.

The ALTER ROLE and ALTER DATABASE commands are used to define per-role and per-database configuration settings.

Lists information about each granted role membership, including assigned options ( ADMIN , INHERIT and/or SET ) and grantor. See the GRANT command for information about role memberships.

By default, only grants to user-created roles are shown; supply the S modifier to include system roles. If pattern is specified, only grants to those roles whose names match the pattern are listed.

Lists replication publications. If pattern is specified, only those publications whose names match the pattern are listed. If + is appended to the command name, the tables and schemas associated with each publication are shown as well.

Lists replication subscriptions. If pattern is specified, only those subscriptions whose names match the pattern are listed. If + is appended to the command name, additional properties of the subscriptions are shown.

Lists data types. If pattern is specified, only types whose names match the pattern are listed. If + is appended to the command name, each type is listed with its internal name and size, its allowed values if it is an enum type, and its associated permissions. By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects.

Lists database roles. (Since the concepts of “ users ” and “ groups ” have been unified into “ roles ” , this command is now equivalent to \dg .) By default, only user-created roles are shown; supply the S modifier to include system roles. If pattern is specified, only those roles whose names match the pattern are listed. If the form \du+ is used, additional information is shown about each role; currently this adds the comment for each role.

Lists installed extensions. If pattern is specified, only those extensions whose names match the pattern are listed. If the form \dx+ is used, all the objects belonging to each matching extension are listed.

Lists extended statistics. If pattern is specified, only those extended statistics whose names match the pattern are listed.

The status of each kind of extended statistics is shown in a column named after its statistic kind (e.g. Ndistinct). defined means that it was requested when creating the statistics, and NULL means it wasn't requested. You can use pg_stats_ext if you'd like to know whether ANALYZE was run and statistics are available to the planner.

Lists event triggers. If pattern is specified, only those event triggers whose names match the pattern are listed. If + is appended to the command name, each object is listed with its associated description.

If filename is specified, the file is edited; after the editor exits, the file's content is copied into the current query buffer. If no filename is given, the current query buffer is copied to a temporary file which is then edited in the same fashion. Or, if the current query buffer is empty, the most recently executed query is copied to a temporary file and edited in the same fashion.

If you edit a file or the previous query, and you quit the editor without modifying the file, the query buffer is cleared. Otherwise, the new contents of the query buffer are re-parsed according to the normal rules of psql , treating the whole buffer as a single line. Any complete queries are immediately executed; that is, if the query buffer contains or ends with a semicolon, everything up to that point is executed and removed from the query buffer. Whatever remains in the query buffer is redisplayed. Type semicolon or \g to send it, or \r to cancel it by clearing the query buffer.

Treating the buffer as a single line primarily affects meta-commands: whatever is in the buffer after a meta-command will be taken as argument(s) to the meta-command, even if it spans multiple lines. (Thus you cannot make meta-command-using scripts this way. Use \i for that.)

If a line number is specified, psql will position the cursor on the specified line of the file or query buffer. Note that if a single all-digits argument is given, psql assumes it is a line number, not a file name.

See Environment , below, for how to configure and customize your editor.

Prints the evaluated arguments to standard output, separated by spaces and followed by a newline. This can be useful to intersperse information in the output of scripts. For example:

If the first argument is an unquoted -n the trailing newline is not written (nor is the first argument).

If you use the \o command to redirect your query output you might wish to use \qecho instead of this command. See also \warn .

This command fetches and edits the definition of the named function or procedure, in the form of a CREATE OR REPLACE FUNCTION or CREATE OR REPLACE PROCEDURE command. Editing is done in the same way as for \edit . If you quit the editor without saving, the statement is discarded. If you save and exit the editor, the updated command is executed immediately if you added a semicolon to it. Otherwise it is redisplayed; type semicolon or \g to send it, or \r to cancel.

The target function can be specified by name alone, or by name and arguments, for example foo(integer, text) . The argument types must be given if there is more than one function of the same name.

If no function is specified, a blank CREATE FUNCTION template is presented for editing.

If a line number is specified, psql will position the cursor on the specified line of the function body. (Note that the function body typically does not begin on the first line of the file.)

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \ef , and neither variable interpolation nor backquote expansion are performed in the arguments.

Sets the client character set encoding. Without an argument, this command shows the current encoding.

Repeats the most recent server error message at maximum verbosity, as though VERBOSITY were set to verbose and SHOW_CONTEXT were set to always .

This command fetches and edits the definition of the named view, in the form of a CREATE OR REPLACE VIEW command. Editing is done in the same way as for \edit . If you quit the editor without saving, the statement is discarded. If you save and exit the editor, the updated command is executed immediately if you added a semicolon to it. Otherwise it is redisplayed; type semicolon or \g to send it, or \r to cancel.

If no view is specified, a blank CREATE VIEW template is presented for editing.

If a line number is specified, psql will position the cursor on the specified line of the view definition.

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \ev , and neither variable interpolation nor backquote expansion are performed in the arguments.

Sets the field separator for unaligned query output. The default is the vertical bar ( | ). It is equivalent to \pset fieldsep .

Sends the current query buffer to the server for execution.

If parentheses appear after \g , they surround a space-separated list of option = value formatting-option clauses, which are interpreted in the same way as \pset option value commands, but take effect only for the duration of this query. In this list, spaces are not allowed around = signs, but are required between option clauses. If = value is omitted, the named option is changed in the same way as for \pset option with no explicit value .

If a filename or | command argument is given, the query's output is written to the named file or piped to the given shell command, instead of displaying it as usual. The file or command is written to only if the query successfully returns zero or more tuples, not if the query fails or is a non-data-returning SQL command.

If the current query buffer is empty, the most recently sent query is re-executed instead. Except for that behavior, \g without any arguments is essentially equivalent to a semicolon. With arguments, \g provides a “ one-shot ” alternative to the \o command, and additionally allows one-shot adjustments of the output formatting options normally set by \pset .

When the last argument begins with | , the entire remainder of the line is taken to be the command to execute, and neither variable interpolation nor backquote expansion are performed in it. The rest of the line is simply passed literally to the shell.

Shows the description (that is, the column names and data types) of the result of the current query buffer. The query is not actually executed; however, if it contains some type of syntax error, that error will be reported in the normal way.

If the current query buffer is empty, the most recently sent query is described instead.

Gets the value of the environment variable env_var and assigns it to the psql variable psql_var . If env_var is not defined in the psql process's environment, psql_var is not changed. Example:

Sends the current query buffer to the server, then treats each column of each row of the query's output (if any) as an SQL statement to be executed. For example, to create an index on each column of my_table :

The generated queries are executed in the order in which the rows are returned, and left-to-right within each row if there is more than one column. NULL fields are ignored. The generated queries are sent literally to the server for processing, so they cannot be psql meta-commands nor contain psql variable references. If any individual query fails, execution of the remaining queries continues unless ON_ERROR_STOP is set. Execution of each query is subject to ECHO processing. (Setting ECHO to all or queries is often advisable when using \gexec .) Query logging, single-step mode, timing, and other query execution features apply to each generated query as well.

If the current query buffer is empty, the most recently sent query is re-executed instead.

Sends the current query buffer to the server and stores the query's output into psql variables (see Variables below). The query to be executed must return exactly one row. Each column of the row is stored into a separate variable, named the same as the column. For example:

If you specify a prefix , that string is prepended to the query's column names to create the variable names to use:

If a column result is NULL, the corresponding variable is unset rather than being set.

If the query fails or does not return one row, no variables are changed.

\gx is equivalent to \g , except that it forces expanded output mode for this query, as if expanded=on were included in the list of \pset options. See also \x .

Gives syntax help on the specified SQL command. If command is not specified, then psql will list all the commands for which syntax help is available. If command is an asterisk ( * ), then syntax help on all SQL commands is shown.

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \help , and neither variable interpolation nor backquote expansion are performed in the arguments.

To simplify typing, commands that consists of several words do not have to be quoted. Thus it is fine to type \help alter table .

Turns on HTML query output format. If the HTML format is already on, it is switched back to the default aligned text format. This command is for compatibility and convenience, but see \pset about setting other output options.

Reads input from the file filename and executes it as though it had been typed on the keyboard.

If filename is - (hyphen), then standard input is read until an EOF indication or \q meta-command. This can be used to intersperse interactive input with input from files. Note that Readline behavior will be used only if it is active at the outermost level.

If you want to see the lines on the screen as they are read you must set the variable ECHO to all .

This group of commands implements nestable conditional blocks. A conditional block must begin with an \if and end with an \endif . In between there may be any number of \elif clauses, which may optionally be followed by a single \else clause. Ordinary queries and other types of backslash commands may (and usually do) appear between the commands forming a conditional block.

The \if and \elif commands read their argument(s) and evaluate them as a Boolean expression. If the expression yields true then processing continues normally; otherwise, lines are skipped until a matching \elif , \else , or \endif is reached. Once an \if or \elif test has succeeded, the arguments of later \elif commands in the same block are not evaluated but are treated as false. Lines following an \else are processed only if no earlier matching \if or \elif succeeded.

The expression argument of an \if or \elif command is subject to variable interpolation and backquote expansion, just like any other backslash command argument. After that it is evaluated like the value of an on/off option variable. So a valid value is any unambiguous case-insensitive match for one of: true , false , 1 , 0 , on , off , yes , no . For example, t , T , and tR will all be considered to be true .

Expressions that do not properly evaluate to true or false will generate a warning and be treated as false.

Lines being skipped are parsed normally to identify queries and backslash commands, but queries are not sent to the server, and backslash commands other than conditionals ( \if , \elif , \else , \endif ) are ignored. Conditional commands are checked only for valid nesting. Variable references in skipped lines are not expanded, and backquote expansion is not performed either.

All the backslash commands of a given conditional block must appear in the same source file. If EOF is reached on the main input file or an \include -ed file before all local \if -blocks have been closed, then psql will raise an error.

Here is an example:

The \ir command is similar to \i , but resolves relative file names differently. When executing in interactive mode, the two commands behave identically. However, when invoked from a script, \ir interprets file names relative to the directory in which the script is located, rather than the current working directory.

List the databases in the server and show their names, owners, character set encodings, and access privileges. If pattern is specified, only databases whose names match the pattern are listed. If + is appended to the command name, database sizes, default tablespaces, and descriptions are also displayed. (Size information is only available for databases that the current user can connect to.)

Reads the large object with OID loid from the database and writes it to filename . Note that this is subtly different from the server function lo_export , which acts with the permissions of the user that the database server runs as and on the server's file system.

Use \lo_list to find out the large object's OID .

Stores the file into a PostgreSQL large object. Optionally, it associates the given comment with the object. Example:

The response indicates that the large object received object ID 152801, which can be used to access the newly-created large object in the future. For the sake of readability, it is recommended to always associate a human-readable comment with every object. Both OIDs and comments can be viewed with the \lo_list command.

Note that this command is subtly different from the server-side lo_import because it acts as the local user on the local file system, rather than the server's user and file system.

Shows a list of all PostgreSQL large objects currently stored in the database, along with any comments provided for them. If + is appended to the command name, each large object is listed with its associated permissions, if any.

Deletes the large object with OID loid from the database.

Arranges to save future query results to the file filename or pipe future results to the shell command command . If no argument is specified, the query output is reset to the standard output.

If the argument begins with | , then the entire remainder of the line is taken to be the command to execute, and neither variable interpolation nor backquote expansion are performed in it. The rest of the line is simply passed literally to the shell.

“ Query results ” includes all tables, command responses, and notices obtained from the database server, as well as output of various backslash commands that query the database (such as \d ); but not error messages.

To intersperse text output in between query results, use \qecho .

Print the current query buffer to the standard output. If the current query buffer is empty, the most recently executed query is printed instead.

Changes the password of the specified user (by default, the current user). This command prompts for the new password, encrypts it, and sends it to the server as an ALTER ROLE command. This makes sure that the new password does not appear in cleartext in the command history, the server log, or elsewhere.

Prompts the user to supply text, which is assigned to the variable name . An optional prompt string, text , can be specified. (For multiword prompts, surround the text with single quotes.)

By default, \prompt uses the terminal for input and output. However, if the -f command line switch was used, \prompt uses standard input and standard output.

This command sets options affecting the output of query result tables. option indicates which option is to be set. The semantics of value vary depending on the selected option. For some options, omitting value causes the option to be toggled or unset, as described under the particular option. If no such behavior is mentioned, then omitting value just results in the current setting being displayed.

\pset without any arguments displays the current status of all printing options.

Adjustable printing options are:

The value must be a number. In general, the higher the number the more borders and lines the tables will have, but details depend on the particular format. In HTML format, this will translate directly into the border=... attribute. In most other formats only values 0 (no border), 1 (internal dividing lines), and 2 (table frame) make sense, and values above 2 will be treated the same as border = 2 . The latex and latex-longtable formats additionally allow a value of 3 to add dividing lines between data rows.

Sets the target width for the wrapped format, and also the width limit for determining whether output is wide enough to require the pager or switch to the vertical display in expanded auto mode. Zero (the default) causes the target width to be controlled by the environment variable COLUMNS , or the detected screen width if COLUMNS is not set. In addition, if columns is zero then the wrapped format only affects screen output. If columns is nonzero then file and pipe output is wrapped to that width as well.

Specifies the field separator to be used in CSV output format. If the separator character appears in a field's value, that field is output within double quotes, following standard CSV rules. The default is a comma.

If value is specified it must be either on or off , which will enable or disable expanded mode, or auto . If value is omitted the command toggles between the on and off settings. When expanded mode is enabled, query results are displayed in two columns, with the column name on the left and the data on the right. This mode is useful if the data wouldn't fit on the screen in the normal “ horizontal ” mode. In the auto setting, the expanded mode is used whenever the query output has more than one column and is wider than the screen; otherwise, the regular mode is used. The auto setting is only effective in the aligned and wrapped formats. In other formats, it always behaves as if the expanded mode is off.

Specifies the field separator to be used in unaligned output format. That way one can create, for example, tab-separated output, which other programs might prefer. To set a tab as field separator, type \pset fieldsep '\t' . The default field separator is '|' (a vertical bar).

Sets the field separator to use in unaligned output format to a zero byte.

If value is specified it must be either on or off which will enable or disable display of the table footer (the ( n rows) count). If value is omitted the command toggles footer display on or off.

Sets the output format to one of aligned , asciidoc , csv , html , latex , latex-longtable , troff-ms , unaligned , or wrapped . Unique abbreviations are allowed.

aligned format is the standard, human-readable, nicely formatted text output; this is the default.

unaligned format writes all columns of a row on one line, separated by the currently active field separator. This is useful for creating output that might be intended to be read in by other programs, for example, tab-separated or comma-separated format. However, the field separator character is not treated specially if it appears in a column's value; so CSV format may be better suited for such purposes.

csv format writes column values separated by commas, applying the quoting rules described in RFC 4180 . This output is compatible with the CSV format of the server's COPY command. A header line with column names is generated unless the tuples_only parameter is on . Titles and footers are not printed. Each row is terminated by the system-dependent end-of-line character, which is typically a single newline ( \n ) for Unix-like systems or a carriage return and newline sequence ( \r\n ) for Microsoft Windows. Field separator characters other than comma can be selected with \pset csv_fieldsep .

wrapped format is like aligned but wraps wide data values across lines to make the output fit in the target column width. The target width is determined as described under the columns option. Note that psql will not attempt to wrap column header titles; therefore, wrapped format behaves the same as aligned if the total width needed for column headers exceeds the target.

The asciidoc , html , latex , latex-longtable , and troff-ms formats put out tables that are intended to be included in documents using the respective mark-up language. They are not complete documents! This might not be necessary in HTML , but in LaTeX you must have a complete document wrapper. The latex format uses LaTeX 's tabular environment. The latex-longtable format requires the LaTeX longtable and booktabs packages.

Sets the border line drawing style to one of ascii , old-ascii , or unicode . Unique abbreviations are allowed. (That would mean one letter is enough.) The default setting is ascii . This option only affects the aligned and wrapped output formats.

ascii style uses plain ASCII characters. Newlines in data are shown using a + symbol in the right-hand margin. When the wrapped format wraps data from one line to the next without a newline character, a dot ( . ) is shown in the right-hand margin of the first line, and again in the left-hand margin of the following line.

old-ascii style uses plain ASCII characters, using the formatting style used in PostgreSQL 8.4 and earlier. Newlines in data are shown using a : symbol in place of the left-hand column separator. When the data is wrapped from one line to the next without a newline character, a ; symbol is used in place of the left-hand column separator.

unicode style uses Unicode box-drawing characters. Newlines in data are shown using a carriage return symbol in the right-hand margin. When the data is wrapped from one line to the next without a newline character, an ellipsis symbol is shown in the right-hand margin of the first line, and again in the left-hand margin of the following line.

When the border setting is greater than zero, the linestyle option also determines the characters with which the border lines are drawn. Plain ASCII characters work everywhere, but Unicode characters look nicer on displays that recognize them.

Sets the string to be printed in place of a null value. The default is to print nothing, which can easily be mistaken for an empty string. For example, one might prefer \pset null '(null)' .

If value is specified it must be either on or off which will enable or disable display of a locale-specific character to separate groups of digits to the left of the decimal marker. If value is omitted the command toggles between regular and locale-specific numeric output.

Controls use of a pager program for query and psql help output. When the pager option is off , the pager program is not used. When the pager option is on , the pager is used when appropriate, i.e., when the output is to a terminal and will not fit on the screen. The pager option can also be set to always , which causes the pager to be used for all terminal output regardless of whether it fits on the screen. \pset pager without a value toggles pager use on and off.

If the environment variable PSQL_PAGER or PAGER is set, output to be paged is piped to the specified program. Otherwise a platform-dependent default program (such as more ) is used.

When using the \watch command to execute a query repeatedly, the environment variable PSQL_WATCH_PAGER is used to find the pager program instead, on Unix systems. This is configured separately because it may confuse traditional pagers, but can be used to send output to tools that understand psql 's output format (such as pspg --stream ).

If pager_min_lines is set to a number greater than the page height, the pager program will not be called unless there are at least this many lines of output to show. The default setting is 0.

Specifies the record (line) separator to use in unaligned output format. The default is a newline character.

Sets the record separator to use in unaligned output format to a zero byte.

In HTML format, this specifies attributes to be placed inside the table tag. This could for example be cellpadding or bgcolor . Note that you probably don't want to specify border here, as that is already taken care of by \pset border . If no value is given, the table attributes are unset.

In latex-longtable format, this controls the proportional width of each column containing a left-aligned data type. It is specified as a whitespace-separated list of values, e.g., '0.2 0.2 0.6' . Unspecified output columns use the last specified value.

Sets the table title for any subsequently printed tables. This can be used to give your output descriptive tags. If no value is given, the title is unset.

If value is specified it must be either on or off which will enable or disable tuples-only mode. If value is omitted the command toggles between regular and tuples-only output. Regular output includes extra information such as column headers, titles, and various footers. In tuples-only mode, only actual table data is shown.

Sets the border drawing style for the unicode line style to one of single or double .

Sets the column drawing style for the unicode line style to one of single or double .

Sets the header drawing style for the unicode line style to one of single or double .

Sets the maximum width of the header for expanded output to one of full (the default value), column , page , or an integer value .

full : the expanded header is not truncated, and will be as wide as the widest output line.

column : truncate the header line to the width of the first column.

page : truncate the header line to the terminal width.

integer value : specify the exact maximum width of the header line.

Illustrations of how these different formats look can be seen in Examples , below.

There are various shortcut commands for \pset . See \a , \C , \f , \H , \t , \T , and \x .

Quits the psql program. In a script file, only execution of that script is terminated.

This command is identical to \echo except that the output will be written to the query output channel, as set by \o .

Resets (clears) the query buffer.

Print psql 's command line history to filename . If filename is omitted, the history is written to the standard output (using the pager if appropriate). This command is not available if psql was built without Readline support.

Sets the psql variable name to value , or if more than one value is given, to the concatenation of all of them. If only one argument is given, the variable is set to an empty-string value. To unset a variable, use the \unset command.

\set without any arguments displays the names and values of all currently-set psql variables.

Valid variable names can contain letters, digits, and underscores. See Variables below for details. Variable names are case-sensitive.

Certain variables are special, in that they control psql 's behavior or are automatically set to reflect connection state. These variables are documented in Variables , below.

This command is unrelated to the SQL command SET .

Sets the environment variable name to value , or if the value is not supplied, unsets the environment variable. Example:

This command fetches and shows the definition of the named function or procedure, in the form of a CREATE OR REPLACE FUNCTION or CREATE OR REPLACE PROCEDURE command. The definition is printed to the current query output channel, as set by \o .

If + is appended to the command name, then the output lines are numbered, with the first line of the function body being line 1.

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \sf , and neither variable interpolation nor backquote expansion are performed in the arguments.

This command fetches and shows the definition of the named view, in the form of a CREATE OR REPLACE VIEW command. The definition is printed to the current query output channel, as set by \o .

If + is appended to the command name, then the output lines are numbered from 1.

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \sv , and neither variable interpolation nor backquote expansion are performed in the arguments.

Toggles the display of output column name headings and row count footer. This command is equivalent to \pset tuples_only and is provided for convenience.

Specifies attributes to be placed within the table tag in HTML output format. This command is equivalent to \pset tableattr table_options .

With a parameter, turns displaying of how long each SQL statement takes on or off. Without a parameter, toggles the display between on and off. The display is in milliseconds; intervals longer than 1 second are also shown in minutes:seconds format, with hours and days fields added if needed.

Unsets (deletes) the psql variable name .

Most variables that control psql 's behavior cannot be unset; instead, an \unset command is interpreted as setting them to their default values. See Variables below.

Writes the current query buffer to the file filename or pipes it to the shell command command . If the current query buffer is empty, the most recently executed query is written instead.

This command is identical to \echo except that the output will be written to psql 's standard error channel, rather than standard output.

Repeatedly execute the current query buffer (as \g does) until interrupted, or the query fails, or the execution count limit (if given) is reached. Wait the specified number of seconds (default 2) between executions. For backwards compatibility, seconds can be specified with or without an interval= prefix. Each query result is displayed with a header that includes the \pset title string (if any), the time as of query start, and the delay interval.

Sets or toggles expanded table formatting mode. As such it is equivalent to \pset expanded .

Lists tables, views and sequences with their associated access privileges. If a pattern is specified, only tables, views and sequences whose names match the pattern are listed. By default only user-created objects are shown; supply a pattern or the S modifier to include system objects.

This is an alias for \dp ( “ display privileges ” ).

With no argument, escapes to a sub-shell; psql resumes when the sub-shell exits. With an argument, executes the shell command command .

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \! , and neither variable interpolation nor backquote expansion are performed in the arguments. The rest of the line is simply passed literally to the shell.

Shows help information. The optional topic parameter (defaulting to commands ) selects which part of psql is explained: commands describes psql 's backslash commands; options describes the command-line options that can be passed to psql ; and variables shows help about psql configuration variables.

Backslash-semicolon is not a meta-command in the same way as the preceding commands; rather, it simply causes a semicolon to be added to the query buffer without any further processing.

Normally, psql will dispatch an SQL command to the server as soon as it reaches the command-ending semicolon, even if more input remains on the current line. Thus for example entering

will result in the three SQL commands being individually sent to the server, with each one's results being displayed before continuing to the next command. However, a semicolon entered as \; will not trigger command processing, so that the command before it and the one after are effectively combined and sent to the server in one request. So for example

results in sending the three SQL commands to the server in a single request, when the non-backslashed semicolon is reached. The server executes such a request as a single transaction, unless there are explicit BEGIN / COMMIT commands included in the string to divide it into multiple transactions. (See Section 55.2.2.1 for more details about how the server handles multi-query strings.)

The various \d commands accept a pattern parameter to specify the object name(s) to be displayed. In the simplest case, a pattern is just the exact name of the object. The characters within a pattern are normally folded to lower case, just as in SQL names; for example, \dt FOO will display the table named foo . As in SQL names, placing double quotes around a pattern stops folding to lower case. Should you need to include an actual double quote character in a pattern, write it as a pair of double quotes within a double-quote sequence; again this is in accord with the rules for SQL quoted identifiers. For example, \dt "FOO""BAR" will display the table named FOO"BAR (not foo"bar ). Unlike the normal rules for SQL names, you can put double quotes around just part of a pattern, for instance \dt FOO"FOO"BAR will display the table named fooFOObar .

Whenever the pattern parameter is omitted completely, the \d commands display all objects that are visible in the current schema search path — this is equivalent to using * as the pattern. (An object is said to be visible if its containing schema is in the search path and no object of the same kind and name appears earlier in the search path. This is equivalent to the statement that the object can be referenced by name without explicit schema qualification.) To see all objects in the database regardless of visibility, use *.* as the pattern.

Within a pattern, * matches any sequence of characters (including no characters) and ? matches any single character. (This notation is comparable to Unix shell file name patterns.) For example, \dt int* displays tables whose names begin with int . But within double quotes, * and ? lose these special meanings and are just matched literally.

A relation pattern that contains a dot ( . ) is interpreted as a schema name pattern followed by an object name pattern. For example, \dt foo*.*bar* displays all tables whose table name includes bar that are in schemas whose schema name starts with foo . When no dot appears, then the pattern matches only objects that are visible in the current schema search path. Again, a dot within double quotes loses its special meaning and is matched literally. A relation pattern that contains two dots ( . ) is interpreted as a database name followed by a schema name pattern followed by an object name pattern. The database name portion will not be treated as a pattern and must match the name of the currently connected database, else an error will be raised.

A schema pattern that contains a dot ( . ) is interpreted as a database name followed by a schema name pattern. For example, \dn mydb.*foo* displays all schemas whose schema name includes foo . The database name portion will not be treated as a pattern and must match the name of the currently connected database, else an error will be raised.

Advanced users can use regular-expression notations such as character classes, for example [0-9] to match any digit. All regular expression special characters work as specified in Section 9.7.3 , except for . which is taken as a separator as mentioned above, * which is translated to the regular-expression notation .* , ? which is translated to . , and $ which is matched literally. You can emulate these pattern characters at need by writing ? for . , ( R +|) for R * , or ( R |) for R ? . $ is not needed as a regular-expression character since the pattern must match the whole name, unlike the usual interpretation of regular expressions (in other words, $ is automatically appended to your pattern). Write * at the beginning and/or end if you don't wish the pattern to be anchored. Note that within double quotes, all regular expression special characters lose their special meanings and are matched literally. Also, the regular expression special characters are matched literally in operator name patterns (i.e., the argument of \do ).

Advanced Features

psql provides variable substitution features similar to common Unix command shells. Variables are simply name/value pairs, where the value can be any string of any length. The name must consist of letters (including non-Latin letters), digits, and underscores.

To set a variable, use the psql meta-command \set . For example,

sets the variable foo to the value bar . To retrieve the content of the variable, precede the name with a colon, for example:

This works in both regular SQL commands and meta-commands; there is more detail in SQL Interpolation , below.

If you call \set without a second argument, the variable is set to an empty-string value. To unset (i.e., delete) a variable, use the command \unset . To show the values of all variables, call \set without any argument.

The arguments of \set are subject to the same substitution rules as with other commands. Thus you can construct interesting references such as \set :foo 'something' and get “ soft links ” or “ variable variables ” of Perl or PHP fame, respectively. Unfortunately (or fortunately?), there is no way to do anything useful with these constructs. On the other hand, \set bar :foo is a perfectly valid way to copy a variable.

A number of these variables are treated specially by psql . They represent certain option settings that can be changed at run time by altering the value of the variable, or in some cases represent changeable state of psql . By convention, all specially treated variables' names consist of all upper-case ASCII letters (and possibly digits and underscores). To ensure maximum compatibility in the future, avoid using such variable names for your own purposes.

Variables that control psql 's behavior generally cannot be unset or set to invalid values. An \unset command is allowed but is interpreted as setting the variable to its default value. A \set command without a second argument is interpreted as setting the variable to on , for control variables that accept that value, and is rejected for others. Also, control variables that accept the values on and off will also accept other common spellings of Boolean values, such as true and false .

The specially treated variables are:

When on (the default), each SQL command is automatically committed upon successful completion. To postpone commit in this mode, you must enter a BEGIN or START TRANSACTION SQL command. When off or unset, SQL commands are not committed until you explicitly issue COMMIT or END . The autocommit-off mode works by issuing an implicit BEGIN for you, just before any command that is not already in a transaction block and is not itself a BEGIN or other transaction-control command, nor a command that cannot be executed inside a transaction block (such as VACUUM ).

In autocommit-off mode, you must explicitly abandon any failed transaction by entering ABORT or ROLLBACK . Also keep in mind that if you exit the session without committing, your work will be lost.

The autocommit-on mode is PostgreSQL 's traditional behavior, but autocommit-off is closer to the SQL spec. If you prefer autocommit-off, you might wish to set it in the system-wide psqlrc file or your ~/.psqlrc file.

Determines which letter case to use when completing an SQL key word. If set to lower or upper , the completed word will be in lower or upper case, respectively. If set to preserve-lower or preserve-upper (the default), the completed word will be in the case of the word already entered, but words being completed without anything entered will be in lower or upper case, respectively.

The name of the database you are currently connected to. This is set every time you connect to a database (including program start-up), but can be changed or unset.

If set to all , all nonempty input lines are printed to standard output as they are read. (This does not apply to lines read interactively.) To select this behavior on program start-up, use the switch -a . If set to queries , psql prints each query to standard output as it is sent to the server. The switch to select this behavior is -e . If set to errors , then only failed queries are displayed on standard error output. The switch for this behavior is -b . If set to none (the default), then no queries are displayed.

When this variable is set to on and a backslash command queries the database, the query is first shown. This feature helps you to study PostgreSQL internals and provide similar functionality in your own programs. (To select this behavior on program start-up, use the switch -E .) If you set this variable to the value noexec , the queries are just shown but are not actually sent to the server and executed. The default value is off .

The current client character set encoding. This is set every time you connect to a database (including program start-up), and when you change the encoding with \encoding , but it can be changed or unset.

true if the last SQL query failed, false if it succeeded. See also SQLSTATE .

If this variable is set to an integer value greater than zero, the results of SELECT queries are fetched and displayed in groups of that many rows, rather than the default behavior of collecting the entire result set before display. Therefore only a limited amount of memory is used, regardless of the size of the result set. Settings of 100 to 1000 are commonly used when enabling this feature. Keep in mind that when using this feature, a query might fail after having already displayed some rows.

Although you can use any output format with this feature, the default aligned format tends to look bad because each group of FETCH_COUNT rows will be formatted separately, leading to varying column widths across the row groups. The other output formats work better.

If this variable is set to true , a table's access method details are not displayed. This is mainly useful for regression tests.

If this variable is set to true , column compression method details are not displayed. This is mainly useful for regression tests.

If this variable is set to ignorespace , lines which begin with a space are not entered into the history list. If set to a value of ignoredups , lines matching the previous history line are not entered. A value of ignoreboth combines the two options. If set to none (the default), all lines read in interactive mode are saved on the history list.

This feature was shamelessly plagiarized from Bash .

The file name that will be used to store the history list. If unset, the file name is taken from the PSQL_HISTORY environment variable. If that is not set either, the default is ~/.psql_history , or %APPDATA%\postgresql\psql_history on Windows. For example, putting:

in ~/.psqlrc will cause psql to maintain a separate history for each database.

The maximum number of commands to store in the command history (default 500). If set to a negative value, no limit is applied.

The database server host you are currently connected to. This is set every time you connect to a database (including program start-up), but can be changed or unset.

If set to 1 or less, sending an EOF character (usually Control + D ) to an interactive session of psql will terminate the application. If set to a larger numeric value, that many consecutive EOF characters must be typed to make an interactive session terminate. If the variable is set to a non-numeric value, it is interpreted as 10. The default is 0.

The value of the last affected OID, as returned from an INSERT or \lo_import command. This variable is only guaranteed to be valid until after the result of the next SQL command has been displayed. PostgreSQL servers since version 12 do not support OID system columns anymore, thus LASTOID will always be 0 following INSERT when targeting such servers.

The primary error message and associated SQLSTATE code for the most recent failed query in the current psql session, or an empty string and 00000 if no error has occurred in the current session.

When set to on , if a statement in a transaction block generates an error, the error is ignored and the transaction continues. When set to interactive , such errors are only ignored in interactive sessions, and not when reading script files. When set to off (the default), a statement in a transaction block that generates an error aborts the entire transaction. The error rollback mode works by issuing an implicit SAVEPOINT for you, just before each command that is in a transaction block, and then rolling back to the savepoint if the command fails.

By default, command processing continues after an error. When this variable is set to on , processing will instead stop immediately. In interactive mode, psql will return to the command prompt; otherwise, psql will exit, returning error code 3 to distinguish this case from fatal error conditions, which are reported using error code 1. In either case, any currently running scripts (the top-level script, if any, and any other scripts which it may have in invoked) will be terminated immediately. If the top-level command string contained multiple SQL commands, processing will stop with the current command.

The database server port to which you are currently connected. This is set every time you connect to a database (including program start-up), but can be changed or unset.

These specify what the prompts psql issues should look like. See Prompting below.

Setting this variable to on is equivalent to the command line option -q . It is probably not too useful in interactive mode.

The number of rows returned or affected by the last SQL query, or 0 if the query failed or did not report a row count.

The server's version number as a string, for example 9.6.2 , 10.1 or 11beta1 , and in numeric form, for example 90602 or 100001 . These are set every time you connect to a database (including program start-up), but can be changed or unset.

true if the last shell command failed, false if it succeeded. This applies to shell commands invoked via the \! , \g , \o , \w , and \copy meta-commands, as well as backquote ( ` ) expansion. Note that for \o , this variable is updated when the output pipe is closed by the next \o command. See also SHELL_EXIT_CODE .

The exit status returned by the last shell command. 0–127 represent program exit codes, 128–255 indicate termination by a signal, and -1 indicates failure to launch a program or to collect its exit status. This applies to shell commands invoked via the \! , \g , \o , \w , and \copy meta-commands, as well as backquote ( ` ) expansion. Note that for \o , this variable is updated when the output pipe is closed by the next \o command. See also SHELL_ERROR .

When this variable is set to off , only the last result of a combined query ( \; ) is shown instead of all of them. The default is on . The off behavior is for compatibility with older versions of psql.

This variable can be set to the values never , errors , or always to control whether CONTEXT fields are displayed in messages from the server. The default is errors (meaning that context will be shown in error messages, but not in notice or warning messages). This setting has no effect when VERBOSITY is set to terse or sqlstate . (See also \errverbose , for use when you want a verbose version of the error you just got.)

Setting this variable to on is equivalent to the command line option -S .

Setting this variable to on is equivalent to the command line option -s .

The error code (see Appendix A ) associated with the last SQL query's failure, or 00000 if it succeeded.

The database user you are currently connected as. This is set every time you connect to a database (including program start-up), but can be changed or unset.

This variable can be set to the values default , verbose , terse , or sqlstate to control the verbosity of error reports. (See also \errverbose , for use when you want a verbose version of the error you just got.)

These variables are set at program start-up to reflect psql 's version, respectively as a verbose string, a short string (e.g., 9.6.2 , 10.1 , or 11beta1 ), and a number (e.g., 90602 or 100001 ). They can be changed or unset.

SQL Interpolation

A key feature of psql variables is that you can substitute ( “ interpolate ” ) them into regular SQL statements, as well as the arguments of meta-commands. Furthermore, psql provides facilities for ensuring that variable values used as SQL literals and identifiers are properly quoted. The syntax for interpolating a value without any quoting is to prepend the variable name with a colon ( : ). For example,

would query the table my_table . Note that this may be unsafe: the value of the variable is copied literally, so it can contain unbalanced quotes, or even backslash commands. You must make sure that it makes sense where you put it.

When a value is to be used as an SQL literal or identifier, it is safest to arrange for it to be quoted. To quote the value of a variable as an SQL literal, write a colon followed by the variable name in single quotes. To quote the value as an SQL identifier, write a colon followed by the variable name in double quotes. These constructs deal correctly with quotes and other special characters embedded within the variable value. The previous example would be more safely written this way:

Variable interpolation will not be performed within quoted SQL literals and identifiers. Therefore, a construction such as ':foo' doesn't work to produce a quoted literal from a variable's value (and it would be unsafe if it did work, since it wouldn't correctly handle quotes embedded in the value).

One example use of this mechanism is to copy the contents of a file into a table column. First load the file into a variable and then interpolate the variable's value as a quoted string:

(Note that this still won't work if my_file.txt contains NUL bytes. psql does not support embedded NUL bytes in variable values.)

Since colons can legally appear in SQL commands, an apparent attempt at interpolation (that is, :name , :'name' , or :"name" ) is not replaced unless the named variable is currently set. In any case, you can escape a colon with a backslash to protect it from substitution.

The :{? name } special syntax returns TRUE or FALSE depending on whether the variable exists or not, and is thus always substituted, unless the colon is backslash-escaped.

The colon syntax for variables is standard SQL for embedded query languages, such as ECPG . The colon syntaxes for array slices and type casts are PostgreSQL extensions, which can sometimes conflict with the standard usage. The colon-quote syntax for escaping a variable's value as an SQL literal or identifier is a psql extension.

The prompts psql issues can be customized to your preference. The three variables PROMPT1 , PROMPT2 , and PROMPT3 contain strings and special escape sequences that describe the appearance of the prompt. Prompt 1 is the normal prompt that is issued when psql requests a new command. Prompt 2 is issued when more input is expected during command entry, for example because the command was not terminated with a semicolon or a quote was not closed. Prompt 3 is issued when you are running an SQL COPY FROM STDIN command and you need to type in a row value on the terminal.

The value of the selected prompt variable is printed literally, except where a percent sign ( % ) is encountered. Depending on the next character, certain other text is substituted instead. Defined substitutions are:

The full host name (with domain name) of the database server, or [local] if the connection is over a Unix domain socket, or [local: /dir/name ] , if the Unix domain socket is not at the compiled in default location.

The host name of the database server, truncated at the first dot, or [local] if the connection is over a Unix domain socket.

The port number at which the database server is listening.

The database session user name. (The expansion of this value might change during a database session as the result of the command SET SESSION AUTHORIZATION .)

The name of the current database.

Like %/ , but the output is ~ (tilde) if the database is your default database.

If the session user is a database superuser, then a # , otherwise a > . (The expansion of this value might change during a database session as the result of the command SET SESSION AUTHORIZATION .)

The process ID of the backend currently connected to.

In prompt 1 normally = , but @ if the session is in an inactive branch of a conditional block, or ^ if in single-line mode, or ! if the session is disconnected from the database (which can happen if \connect fails). In prompt 2 %R is replaced by a character that depends on why psql expects more input: - if the command simply wasn't terminated yet, but * if there is an unfinished /* ... */ comment, a single quote if there is an unfinished quoted string, a double quote if there is an unfinished quoted identifier, a dollar sign if there is an unfinished dollar-quoted string, or ( if there is an unmatched left parenthesis. In prompt 3 %R doesn't produce anything.

Transaction status: an empty string when not in a transaction block, or * when in a transaction block, or ! when in a failed transaction block, or ? when the transaction state is indeterminate (for example, because there is no connection).

The line number inside the current statement, starting from 1 .

The character with the indicated octal code is substituted.

The value of the psql variable name . See Variables , above, for details.

The output of command , similar to ordinary “ back-tick ” substitution.

Prompts can contain terminal control characters which, for example, change the color, background, or style of the prompt text, or change the title of the terminal window. In order for the line editing features of Readline to work properly, these non-printing control characters must be designated as invisible by surrounding them with %[ and %] . Multiple pairs of these can occur within the prompt. For example:

results in a boldfaced ( 1; ) yellow-on-black ( 33;40 ) prompt on VT100-compatible, color-capable terminals.

Whitespace of the same width as the most recent output of PROMPT1 . This can be used as a PROMPT2 setting, so that multi-line statements are aligned with the first line, but there is no visible secondary prompt.

To insert a percent sign into your prompt, write %% . The default prompts are '%/%R%x%# ' for prompts 1 and 2, and '>> ' for prompt 3.

This feature was shamelessly plagiarized from tcsh .

Command-Line Editing

psql uses the Readline or libedit library, if available, for convenient line editing and retrieval. The command history is automatically saved when psql exits and is reloaded when psql starts up. Type up-arrow or control-P to retrieve previous lines.

You can also use tab completion to fill in partially-typed keywords and SQL object names in many (by no means all) contexts. For example, at the start of a command, typing ins and pressing TAB will fill in insert into . Then, typing a few characters of a table or schema name and pressing TAB will fill in the unfinished name, or offer a menu of possible completions when there's more than one. (Depending on the library in use, you may need to press TAB more than once to get a menu.)

Tab completion for SQL object names requires sending queries to the server to find possible matches. In some contexts this can interfere with other operations. For example, after BEGIN it will be too late to issue SET TRANSACTION ISOLATION LEVEL if a tab-completion query is issued in between. If you do not want tab completion at all, you can turn it off permanently by putting this in a file named .inputrc in your home directory:

(This is not a psql but a Readline feature. Read its documentation for further details.)

The -n ( --no-readline ) command line option can also be useful to disable use of Readline for a single run of psql . This prevents tab completion, use or recording of command line history, and editing of multi-line commands. It is particularly useful when you need to copy-and-paste text that contains TAB characters.

Environment

If \pset columns is zero, controls the width for the wrapped format and width for determining if wide output requires the pager or should be switched to the vertical format in expanded auto mode.

Default connection parameters (see Section 34.15 ).

Specifies whether to use color in diagnostic messages. Possible values are always , auto and never .

Editor used by the \e , \ef , and \ev commands. These variables are examined in the order listed; the first that is set is used. If none of them is set, the default is to use vi on Unix systems or notepad.exe on Windows systems.

When \e , \ef , or \ev is used with a line number argument, this variable specifies the command-line argument used to pass the starting line number to the user's editor. For editors such as Emacs or vi , this is a plus sign. Include a trailing space in the value of the variable if there needs to be space between the option name and the line number. Examples:

The default is + on Unix systems (corresponding to the default editor vi , and useful for many other common editors); but there is no default on Windows systems.

Alternative location for the command history file. Tilde ( ~ ) expansion is performed.

If a query's results do not fit on the screen, they are piped through this command. Typical values are more or less . Use of the pager can be disabled by setting PSQL_PAGER or PAGER to an empty string, or by adjusting the pager-related options of the \pset command. These variables are examined in the order listed; the first that is set is used. If neither of them is set, the default is to use more on most platforms, but less on Cygwin.

When a query is executed repeatedly with the \watch command, a pager is not used by default. This behavior can be changed by setting PSQL_WATCH_PAGER to a pager command, on Unix systems. The pspg pager (not part of PostgreSQL but available in many open source software distributions) can display the output of \watch if started with the option --stream .

Alternative location of the user's .psqlrc file. Tilde ( ~ ) expansion is performed.

Command executed by the \! command.

Directory for storing temporary files. The default is /tmp .

This utility, like most other PostgreSQL utilities, also uses the environment variables supported by libpq (see Section 34.15 ).

Unless it is passed an -X option, psql attempts to read and execute commands from the system-wide startup file ( psqlrc ) and then the user's personal startup file ( ~/.psqlrc ), after connecting to the database but before accepting normal commands. These files can be used to set up the client and/or the server to taste, typically with \set and SET commands.

The system-wide startup file is named psqlrc . By default it is sought in the installation's “ system configuration ” directory, which is most reliably identified by running pg_config --sysconfdir . Typically this directory will be ../etc/ relative to the directory containing the PostgreSQL executables. The directory to look in can be set explicitly via the PGSYSCONFDIR environment variable.

The user's personal startup file is named .psqlrc and is sought in the invoking user's home directory. On Windows the personal startup file is instead named %APPDATA%\postgresql\psqlrc.conf . In either case, this default file path can be overridden by setting the PSQLRC environment variable.

Both the system-wide startup file and the user's personal startup file can be made psql -version-specific by appending a dash and the PostgreSQL major or minor release identifier to the file name, for example ~/.psqlrc-16 or ~/.psqlrc-16.4 . The most specific version-matching file will be read in preference to a non-version-specific file. These version suffixes are added after determining the file path as explained above.

The command-line history is stored in the file ~/.psql_history , or %APPDATA%\postgresql\psql_history on Windows.

The location of the history file can be set explicitly via the HISTFILE psql variable or the PSQL_HISTORY environment variable.

psql works best with servers of the same or an older major version. Backslash commands are particularly likely to fail if the server is of a newer version than psql itself. However, backslash commands of the \d family should work with servers of versions back to 9.2, though not necessarily with servers newer than psql itself. The general functionality of running SQL commands and displaying query results should also work with servers of a newer major version, but this cannot be guaranteed in all cases.

If you want to use psql to connect to several servers of different major versions, it is recommended that you use the newest version of psql . Alternatively, you can keep around a copy of psql from each major version and be sure to use the version that matches the respective server. But in practice, this additional complication should not be necessary.

Before PostgreSQL 9.6, the -c option implied -X ( --no-psqlrc ); this is no longer the case.

Before PostgreSQL 8.4, psql allowed the first argument of a single-letter backslash command to start directly after the command, without intervening whitespace. Now, some whitespace is required.

Notes for Windows Users

psql is built as a “ console application ” . Since the Windows console windows use a different encoding than the rest of the system, you must take special care when using 8-bit characters within psql . If psql detects a problematic console code page, it will warn you at startup. To change the console code page, two things are necessary:

Set the code page by entering cmd.exe /c chcp 1252 . (1252 is a code page that is appropriate for German; replace it with your value.) If you are using Cygwin, you can put this command in /etc/profile .

Set the console font to Lucida Console , because the raster font does not work with the ANSI code page.

The first example shows how to spread a command over several lines of input. Notice the changing prompt:

Now look at the table definition again:

Now we change the prompt to something more interesting:

Let's assume you have filled the table with data and want to take a look at it:

You can display tables in different ways by using the \pset command:

Alternatively, use the short commands:

Also, these output format options can be set for just one query by using \g :

Here is an example of using the \df command to find only functions with names matching int*pl and whose second argument is of type bigint :

When suitable, query results can be shown in a crosstab representation with the \crosstabview command:

This second example shows a multiplication table with rows sorted in reverse numerical order and columns with an independent, ascending numerical order.


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If you see anything in the documentation that is not correct, does not match your experience with the particular feature or requires further clarification, please use this form to report a documentation issue.

Declaring and Assigning Variables in PostgreSQL: A Troubleshooting Guide

Abstract: Having trouble declaring and assigning variables in PostgreSQL? Learn about common error messages and how to troubleshoot them in this guide.

Declaring and Assigning Variables in PostgreSQL: Troubleshooting Guide

In this article, we will explore how to declare and assign variables in PostgreSQL, as well as troubleshoot common issues that may arise. We will cover key concepts, applications, and the significance of declaring and assigning variables in PostgreSQL. This guide is aimed at those who have some experience with PostgreSQL and are looking to deepen their understanding of this important feature.

Key Concepts

In PostgreSQL, variables are used to store values that can be referenced and used in SQL statements. There are two types of variables in PostgreSQL: plpgsql variables and sql variables. plpgsql variables are used in PL/pgSQL functions and procedures, while sql variables are used in SQL statements.

To declare a variable in PostgreSQL, you can use the DECLARE statement followed by the variable name and data type. For example:

To assign a value to a variable, you can use the := operator. For example:

Troubleshooting Common Issues

One common issue that may arise when trying to declare and assign a variable in PostgreSQL is the following error message:

This error occurs because the := operator is not supported in sql variables. Instead, you should use the = operator. For example:

Applications and Significance

Declaring and assigning variables in PostgreSQL is an important feature that has many applications. For example, you can use variables to store intermediate results in complex queries, or to pass values between different parts of a PL/pgSQL function or procedure. By understanding how to declare and assign variables in PostgreSQL, you will be able to write more efficient and effective SQL statements.

Variables in PostgreSQL are used to store values that can be referenced and used in SQL statements.
There are two types of variables in PostgreSQL: plpgsql variables and sql variables.
To declare a variable in PostgreSQL, use the DECLARE statement followed by the variable name and data type.
To assign a value to a variable, use the = operator for sql variables and the := operator for plpgsql variables.
Understanding how to declare and assign variables in PostgreSQL is important for writing efficient and effective SQL statements.
PostgreSQL PL/pgSQL Declarations
PostgreSQL PL/pgSQL Variables
PostgreSQL PL/pgSQL SQL Statements

Tags: : PostgreSQL variables SQL database development

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PostgreSQL Variables

Updated May 12, 2023

Introduction to PostgreSQL Variables

The PostgreSQL variable is a convenient name or an abstract name given to the memory location. The variable always has a particular data-type give to it, like boolean, text, char, integer, double precision, date, time, etc. They are used to store the data which can be changed. The PostgreSQL variables are initialized to the NULL value if they are not defined with a DEFAULT value. We can modify the value stored within the variable by using the function or code block. We can store the data temporarily in the variable during the function execution.

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Consider the following syntax to declare a variable:

Explanation:

var_name: The variable name to assign.
CONSTANT: This is an optional component. If we have defined the CONSTANT, we can not change the variable’s value once the variable has been initialized.
data-type: The variable data-type to assign.
NOT NULL: This is an optional component. If we have defined the NOT NULL, then the variable can not have a NULL value.
initial_value: This is an optional component. By using this, we can initialize the variable while creating the variable. If we have not defined the initial_value, then the variable will be assigned with the NULL value.

How to Initialize Variables in PostgreSQL?

There are various ways to initialize the variables that are given as follows:

1. While the creation

We can initialize the variable while creating the variable by giving an initial value.

Consider the following example to understand the variable initialization.

The above example would declare a PostgreSQL variable of name num_of_students having initial_value as 100 and data-type as an integer.

2. After creation

We can declare a variable first, and then we can initialize the variable.

Consider the following example to understand the variable initialization after creation.

The above example would declare a PostgreSQL variable of name num_of_students having data-type as an integer.

Now we will initialize the variable by using the following statement:

The above statement would initialize a PostgreSQL variable of name num_of_students with a value of 300.

How to Declare Variables in PostgreSQL?

There are various ways to declare the variable that is given as follows:

1. DECLARE with initial_value

Consider the following example to understand the variable declaration with initial_value.

The above example would declare a PostgreSQL variable of name name_of_student having data-type as VARCHAR and initial_value as ‘John’.

2. DECLARE without initial_value

Consider the following example to understand the variable declaration without an initial value.

The above example would declare a PostgreSQL variable of name name_of_student having data-type as VARCHAR.

3. DECLARE CONSTANT variable

Consider the following example to understand the variable declaration with an initial value and as a CONSTANT.

The above example would declare a PostgreSQL variable of name name_of_student having data-type as VARCHAR and having an initial value as ‘John’, which will be changed further as it is specified as CONSTANT.

How do Variables work?

All of the PostgreSQL variables we use in the function must be defined within the DECLARE keyword.
During the execution of the function, we can temporarily store the data in the variable.
We can modify the data stored within the variable.
We cannot change the variable’s value if any of the PostgreSQL variables is defined as the CONSTANT.
If a PostgreSQL variable is not specified as CONSTANT, we can declare it with a default value and change it later as necessary.

Examples of PostgreSQL Variables

Given below are the examples:

Gives initial value to a PostgreSQL variable.

a. Without DEFAULT keyword

Consider the following function of the name:

Now we will execute the above function.

Illustrate the following SQL statement and snapshot the result of the above function.

b. With default keyword

c. CONSTANT variable

without DEFAULT keyword

With default keyword

Illustrate the following SQL statement and snapshot to understand the result of the above function:

Gives a value to a PostgreSQL variable after declaration.

Illustrate the following SQL statement and a snapshot of the above function:

Integrate a Serverless SQL Database with Vercel Postgres

Vercel now offers different types of databases that are streamlined into its workflow. In this article, we will focus on one of the databases—Vercel Postgres. We will go through its key features and setup process and show how to interact with it using the Vercel Postgres SDK and Prisma ORM.

Vercel is positioning itself as a platform that abstracts infrastructure management, allowing developers to focus exclusively on building modern web applications. The introduction of Vercel Storage , a suite of managed serverless storage products that seamlessly integrates with popular frontend frameworks.

Moving away from depending on external database services, Vercel now offers different types of databases that are streamlined into its workflow. This addition significantly improves the developer experience, efficiency and scalability.

In this article, we will focus on one of the databases— Vercel Postgres . We will go through its key features and setup process and show how to interact with it using the Vercel Postgres SDK and Prisma ORM . In the end, you will have the knowledge you need to leverage the power of Vercel Postgres for efficient data management in your Vercel projects.

Prerequisites

This guide assumes you have a basic knowledge of React and Next.js .

Vercel Postgres

Vercel Postgres was introduced as one of the quartets that include Vercel KV, Vercel Blob and Vercel Edge Config. It is a serverless SQL database for storing structured and relational data. It enables the creation of scalable, secure PostgreSQL databases designed to integrate with Vercel functions.

Though a partnership with Neon DB powers Vercel Postgres, all operations, such as creating, deleting and managing Postgres, happen within the Vercel dashboard. So you won’t need to create a Neon account to use Vercel Postgres.

Vercel Postgres offers several benefits, making it an attractive choice for developers working with Vercel. Let’s take a look at some notable ones:

Serverless and scalable: Vercel Postgres is serverless and automatically scales to meet your application’s needs, eliminating the need to provide and manage database resources.
Streamlined workflow: By offering integrated database solutions, Vercel Postgres creates a more unified development environment. This encourages developers to stay within the Vercel ecosystem throughout the entire project.
SQL support: Vercel Postgres allows developers to interact with their data using the powerful and familiar SQL language.
High security standards: Vercel implements robust security measures to better safeguard your data.
Integration with ORMs: In addition to its SDK, Vercel Postgres also supports integration with popular Object-Relational Mapping (ORM) tools like Prisma and Drizzle.

As mentioned previously, Vercel Postgres is only one of the recently introduced databases. You can find more information about Vercel storage and other available databases in the docs .

Project Setup

Run the command below to create a Next.js application:

This creates a Next.js application and configures it based on specific prompts. Select the options highlighted in the image below.

To use Vercel Postgres with an application, we need to first add the application to Vercel. To do that, we would upload the project to GitHub and then connect it to Vercel.

To push your demo application to your GitHub account, follow the steps below:

If you do not already have a GitHub account, create one . If you do, sign in .
Once you are signed in, click new on the console to register a new repository.
Enter a preferred name and description for your project, then click Create Repository.
To complete the push to GitHub, run the commands provided on the subsequent page in the terminal of the demo project.

For additional information on how to upload a project to GitHub, click here .

Configuring Vercel Postgres

Next, let’s connect the application we have uploaded to Vercel. If you do not have a Vercel account, you can create one . If you’re already a user, just log in . Once you have completed onboarding, add a new project by clicking the Add new button on the dashboard console. This will allow you to add a new project from your GitHub repository.

Next, select the uploaded demo project from your list of repositories. Assign a name to the project, then click “Deploy.” This will deploy your application to Vercel.

After a successful deployment, you should see a new page with a congratulatory message and a link to your newly deployed application.

Select “Continue to Dashboard,” then proceed to create the database.

From the dashboard header, click “Storage,” then “Create Database.” A modal will appear, listing the various databases that Vercel offers.

Select “Postgres” from the list and continue by selecting the default configuration option for the rest of the resulting prompts. Now we’ve successfully connected the database to our project.

To integrate this database with our demo project, we’ll need some credentials. These include the API URL, host, password and others, which are pre-generated and provided as environment variables once the database is connected to a deployed project.

Click on “Settings” on the dashboard’s header, then select “Environment Variables” from the sidebar to see the list of predefined environment variables:

Next, let’s create an interaction pipeline between the demo application and the database. Run the following command in the terminal to install the latest version of Vercel CLI:

This enables us to run Vercel commands in the terminal.

Also, run the command below to install the Vercel Postgres SDK:

The SDK provides an efficient way to interact with the Postgres database. In the next section, we will discuss how to use the SDK.

Run the following command to import the predefined environment variables into our local project so they can be used to access the database:

This creates a .env.development.local file in our demo project and populates it with the environment variable definitions.

Having done that, we’ve successfully set up and integrated our Vercel Postgres database. In the next section, we will see how to interact with this database.

Interacting with the Database

There are two main ways to access the database from the demo application:

Through the Vercel Postgres SDK
Through one of the supported ORMs

The Vercel Postgres SDK

The SDK abstracts the complexities of accessing the database and provides tools for efficient interaction with the Postgres database. The SDK is compatible with the node-postgres library and offers the following options:

createClient()

The sql function, imported from the Vercel Postgres SDK, is designed to automatically create a pooled database connection using the URL specified in the environment variables.

Unlike generic functions invoked with parentheses, the sql function is defined as a template literal tag. It isn’t called using parentheses. Instead, it is suffixed with a template literal string that defines a particular SQL query.

This is what the syntax looks like:

The code snippet above shows how to construct SQL queries using the sql template literal tag. This function then converts the query into a native Postgres parameterized query.

This approach is used to help prevent the possibility of SQL injections. An error will be thrown if you try to call the sql function like a regular function. Learn about how the function is processed under the hood.

To see this in action, ensure the development server is running or run the command below in the terminal to restart it:

Create a new file named route.ts within the api/test directory and add the following code to it:

This creates an API route. When visited, it adds a Pets table in the database.

Visit this route in your browser using http://localhost:3000/api/test and see the response shown below. This indicates that the table has been created successfully.

The table you’ve created will be instantly visible on the Vercel dashboard. To view it, go to the dashboard page, click “Data” from the sidebar, and then select the newly created table—in this case, it’s called “Pets.” The table should be empty.

To add data to the created table, create a new file named addPet/route.ts in the app/api/ folder and add the following to it:

Here, we defined a new API route that adds a row into the Pets table. The ownerName and petName fields are taken from the query string embedded in the URL. The route returns the entire table as a response.

To see the response as shown below, go to http://localhost:3000/api/add-pet?petName=Johnny&ownerName=Mark in your browser.

Also, refresh the table in the dashboard to see the data that was added.

Somewhat similar to how the SQL function works, the Vercel SDK also provides a db helper method. that can be used to create a client to connect to a Vercel Postgres database.

The db helper method is particularly useful when there are multiple queries or transactions that need to be processed, as it maintains the connection, unlike the SQL helper which will connect for each query.

Here is a sample code snippet of how it works:

Here, we can see how we can create a client instance and call the sql method on it for subsequent SQL queries.

The createClient() function allows us to create, connect and disconnect connections for individual clients for each query. However, this approach isn’t as efficient as the previous ones and should be used only when a single client is needed.

The following is a sample code snippet showing how to use the createClient() method:

Using One of the Supported ORMs

We can avoid the stress of writing complex SQL queries directly and rely solely on an ORM. ORMs are abstractions that simplify data access and manipulation for developers. It allows interaction with a database using the familiar syntax of your programming language.

Vercel Postgres supports ORMs like Kysely, Drizzle and Prisma. Let’s take a look at the Prisma ORM integration.

To use Vercel Postgres with Prisma, we need to start by installing the Prisma CLI and Prisma client. Run the following commands in your terminal:

Next, run the command below to initialize a new Prisma project within your current working directory:

This command creates a new prisma folder at the root level of the application. This folder contains a schema.prisma file, which contains Prisma’s base configuration.

Next, you can use the environment variables in the schema.prisma file as shown below:

The code above configures the Prisma ORM and also defines a User model. This article only provides an overview of how to use the ORM and won’t dive into the syntax of Prisma. You can learn more about how Prisma works from the official documentation .

Next, run the command below to synchronize the model defined in the schema.prisma file with a Vercel Postgres database:

Also, run the command below to generate the types:

Finally, we can use @prisma/client to query the Vercel Postgres database as shown below:

The code snippet above shows how Prisma ORM allows us to interact with the database without writing SQL queries directly, which is a more intuitive approach.

This article provides a comprehensive introduction to Vercel Postgres, including detailed steps for configuring the database. It also provides an overview of how to interact with the database using the SDK or an ORM.

Ifeoma Imoh

Ifeoma Imoh is a software developer and technical writer who is in love with all things JavaScript. Find her on Twitter or YouTube .

How to deploy a react app with vercel and github—a step-by-step guide, how to optimize file management in next.js, all articles.

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Postgresql - How to set variable value in function

I'm trying to set value of a variable based on case statement and return the data as a table in Postgres function.

In the case statement I'm trying to do bitwise operation on options field

This is not working. Can anybody tell me what is wrong in this ?

It shows the following error

ERROR: structure of query does not match function result type DETAIL: Returned type boolean does not match expected type text in column 2. CONTEXT: PL/pgSQL function get_ticket_types() line 7 at RETURN QUERY ********** Error **********

stored-procedures

2 Answers 2

Create a text function to get concatenated type names from options:

and use it in this way:

If anyone is getting error ERROR: syntax error at or near "text" , make sure that the function language is plpgsql .

Had the same problem

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PostgreSQL Variables

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COMMENTS

How do you use variables in a simple PostgreSQL script?
16. Here's an example of using a variable in plpgsql: create table test (id int); insert into test values (1); insert into test values (2); insert into test values (3); create function test_fn() returns int as $$. declare val int := 2; begin.
PL/pgSQL Variables
variable_name data_type [= expression]; Code language: PostgreSQL SQL dialect and PL/pgSQL (pgsql) In this syntax: First, specify the name of the variable. It is a good practice to assign a meaningful name to a variable. For example, instead of naming a variable i you should use index or counter. Second, associate a specific data type with the ...
PostgreSQL: Documentation: 16: 43.5. Basic Statements
An assignment of a value to a PL/pgSQL variable is written as:. variable { := | = } expression; . As explained previously, the expression in such a statement is evaluated by means of an SQL SELECT command sent to the main database engine. The expression must yield a single value (possibly a row value, if the variable is a row or record variable).
PostgreSQL: Declaring Variables
This PostgreSQL tutorial explains how to declare variables in PostgreSQL with syntax and examples. In PostgreSQL, a variable allows a programmer to store data temporarily during the execution of code. ... The name to assign to the variable. CONSTANT Optional. If specified, the value of the variable can not be changed after the variable has been ...
How to Use Variables in PostgreSQL
In the section called DECLARE, you need to tell the script what your variable is and what was its type. In PL/SQL, there are two parts. One is the declaration, and another is the script part, where standard SQL is written. The format is like the following. DO $$. DECLARE variable_name <TYPE>.
How to declare variables in PL/pgSQL stored procedures
Variable Assignment: Any value as accepted by data type, constant, or expression can be assigned to the variable. This part is optional. ... Another way to use %ROWTYPE in PostgreSQL variables is using RECORD as the data type of a variable. Below is the same example as above, but displaying "emp" table data using RECORD type. ...
How to Declare a Variable in PostgreSQL
Here is the syntax to declare a variable in Postgres: DECLARE var_name < CONSTANT > data_type < NOT NULL > < { DEFAULT | := } expression >; In this syntax: - The " var_name " represents a meaningful name that will be assigned to a variable. - " CONSTANT " is an optional parameter, used to assign a non-changeable value to the given ...
PostgreSQL: Documentation: 16: 43.3. Declarations
newname ALIAS FOR oldname; . The ALIAS syntax is more general than is suggested in the previous section: you can declare an alias for any variable, not just function parameters. The main practical use for this is to assign a different name for variables with predetermined names, such as NEW or OLD within a trigger function.. Examples: DECLARE prior ALIAS FOR old; updated ALIAS FOR new;
PostgreSQL
In PostgreSQL, the select into statement to select data from the database and assign it to a variable. Syntax: select select_list into variable_name from table_expression; In this syntax, one can place the variable after the into keyword. The select into statement will assign the data returned by the select clause to the variable. Besides selecting
How to use a postgres variable in the select clause
With MSSQL it's easy, the @ marking the start of all variable names allows the parser to know that it is a variable not a column. This is useful for things like injecting constant values where a select is providing the input to an insert table when copying from a staging table. declare @foo varchar(50) = 'bar'; select @foo;
PL/pgSQL SELECT INTO Statement
In this syntax, First, specify one or more columns from which you want to retrieve data in the select clause. Second, place one or more variables after the into keyword. Third, provide the name of the table in the from clause. The select into statement will assign the data returned by the select clause to the corresponding variables.
Storing Select Query Results in Variables in PostgreSQL
In PostgreSQL, you can assign the results of a SELECT query to variables for further processing. This can be useful when you want to store specific values from a query result and use them later in your code. To assign the results of a SELECT query to variables, you can use the SELECT INTO statement. This statement allows you to retrieve ...
PostgreSQL: Documentation: 16: psql
Perform a variable assignment, like the \set meta-command. Note that you must separate name and value, if any, by an equal sign on the command line. ... Before PostgreSQL 8.4, psql allowed the first argument of a single-letter backslash command to start directly after the command, without intervening whitespace. Now, some whitespace is required ...
Declaring and Assigning Variables in PostgreSQL: A Troubleshooting Guide
To declare a variable in PostgreSQL, use the DECLARE statement followed by the variable name and data type. To assign a value to a variable, use the = operator for sql variables and the := operator for plpgsql variables. Understanding how to declare and assign variables in PostgreSQL is important for writing efficient and effective SQL statements.
How to Initialize, Declare Variables in PostgreSQL?
We can initialize the variable while creating the variable by giving an initial value. Consider the following example to understand the variable initialization. Code: DECLARE num_of_students integer : = 100; or. DECLARE num_of_students integer DEFAULT 100; The above example would declare a PostgreSQL variable of name num_of_students having ...
How to use variables in a raw postgresql script block, outside ...
You may have come across the problem that you cannot just declare your variables in a place somewhere in your postgres script and start using them as you would do for example in Microsoft SQL (perhaps with Management Studio), without having to declare the variables within the context of a postrges function, or some kind of code block...
postgresql
You cannot use SET to assign a variable. That's taken to be the SQL command SET for setting run-time parameters. But you can assign a variable at declaration time, even use a subquery for that. @a_horse_with_no_name already wrote about naming conflicts. Using a clean format goes a long way when debugging code ...
Integrate a Serverless SQL Database with Vercel Postgres
The sql function, imported from the Vercel Postgres SDK, is designed to automatically create a pooled database connection using the URL specified in the environment variables. Unlike generic functions invoked with parentheses, the sql function is defined as a template literal tag.
Postgresql assign a select query to variable in the function
Postgresql assign a select query to variable in the function. Ask Question Asked 10 years, 10 months ago. Modified 10 years, 10 months ago. ... Use SELECT only when you need a query to data, not for function or variable evaluation! Share. Improve this answer. Follow edited Oct 10, 2013 at 7:34. answered Oct ...
Postgresql
I'm trying to set value of a variable based on case statement and return the data as a table in Postgres function. ... Setting variable in a Postgres function. 0. Specify parameter when assigning value in PostgreSQL function. 0. Call a FUNCTION from inside a PROCEDURE in PostgreSQL. 0.

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Declaring and Assigning Variables in PostgreSQL: A Troubleshooting Guide

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