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# PL/pgSQL While Loop

**Summary**: in this tutorial, you will learn how to use PL/pgSQL `while` loop statement to execute statements as long as a condition is true.

## Introduction to PL/pgSQL while loop statement

The `while` loop statement executes one or more statements as long as a specified condition is true.

Here's the basic syntax of a `while` loop statement:

```sql
[ <<label>> ]
while condition loop
   statements;
end loop;
```

In this syntax, PostgreSQL evaluates the `condition` before executing the `statements`.

If the condition is true, it executes the `statements`. After each iteration, the `while` loop evaluates the `codition` again.

Inside the body of the `while` loop, you need to change the some [variables](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-variables) to make the `condition` `false` or `null` at some points. Otherwise, you will have an indefinite loop.

Because the `while` loop tests the `condition` before executing the `statements`, it is often referred to as a **pretest loop**.

The following flowchart illustrates the `while` loop statement:

![PL/pgSQL WHILE loop](https://neon.com/postgresqltutorial/plpgsql-WHILE-loop.png)

## PL/pgSQL while loop example

The following example uses the `while` loop statement to display the value of a `counter`:

```plsql
do $$

declare
	counter integer := 0;
begin
	while counter < 5 loop
		raise notice 'Counter %', counter;
		counter := counter + 1;
	end loop;
end;

$$;
```

Output:

```
NOTICE:  Counter 0
NOTICE:  Counter 1
NOTICE:  Counter 2
NOTICE:  Counter 3
NOTICE:  Counter 4
```

How it works.

- First, declare the `counter` variable and initialize its value to 0.
- Second, use the `while` loop statement to show the current value of the `counter` as long as it is less than 5. In each iteration, increase the value of `counter` by one. After 5 iterations, the `counter` is 5 therefore the `while` loop is terminated.

## Summary

- Use the PL/pgSQL `while` loop statement to execute one or more statements as long as long as a specified condition is true.

---

## Related docs (PostgreSQL PL/pgSQL)

- [Introduction](https://neon.com/postgresql/postgresql-plpgsql/introduction-to-postgresql-stored-procedures)
- [Block Structure](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-block-structure)
- [Variables](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-variables)
- [Constants](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-constants)
- [IF-ELSE Statements](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-if-else-statements)
- [CASE Statement](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-case-statement)
- [Loop Statements](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-loop-statements)
- [FOR Loop](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-for-loop)
- [EXIT Statement](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-exit)
- [CONTINUE Statement](https://neon.com/postgresql/postgresql-plpgsql/pl-pgsql-continue)
- [Cursor](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-cursor)
- [Function Parameters](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-function-parameters)
- [Function Overloading](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-function-overloading)
- [Function Returns Table](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-function-returns-a-table)
- [Returns SETOF](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-returns-setof)
- [Record Types](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-record-types)
- [Row Types](https://neon.com/postgresql/postgresql-plpgsql/pl-pgsql-row-types)
- [Error Messages](https://neon.com/postgresql/postgresql-plpgsql/plpgsql-errors-messages)
- [Exception Handling](https://neon.com/postgresql/postgresql-plpgsql/postgresql-exception)
- [CREATE FUNCTION](https://neon.com/postgresql/postgresql-plpgsql/postgresql-create-function)
- [CREATE PROCEDURE](https://neon.com/postgresql/postgresql-plpgsql/postgresql-create-procedure)
- [DROP FUNCTION](https://neon.com/postgresql/postgresql-plpgsql/postgresql-drop-function)
- [DROP PROCEDURE](https://neon.com/postgresql/postgresql-plpgsql/postgresql-drop-procedure)
- [Stored Procedure with INOUT Parameters](https://neon.com/postgresql/postgresql-plpgsql/postgresql-stored-procedure-with-inout-parameters)
- [Introduction to Stored Procedures](https://neon.com/postgresql/postgresql-plpgsql/introduction-to-postgresql-stored-procedures)
- [SELECT INTO](https://neon.com/postgresql/postgresql-plpgsql/pl-pgsql-select-into)
- [ASSERT Statement](https://neon.com/postgresql/postgresql-plpgsql/pl-pgsql-assert)
- [Dollar-Quoted String Constants](https://neon.com/postgresql/postgresql-plpgsql/dollar-quoted-string-constants)