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# CASE

## Synopsis

Simple case:

```text theme={null}
CASE
  WHEN condition THEN statements
  [ ... ]
  [ ELSE statements ]
END CASE
```

Searched case:

```text theme={null}
CASE expression
  WHEN expression THEN statements
  [ ... ]
  [ ELSE statements ]
END
```

## Description

The `CASE` statement is an optional construct to allow conditional processing
in [SQL routines](/sql/routines/introduction).

The `WHEN` clauses are evaluated sequentially, stopping after the first match,
and therefore the order of the statements is significant. The statements of the
`ELSE` clause are executed if none of the `WHEN` clauses match.

Unlike other languages like C or Java, SQL does not support case fall through,
so processing stops at the end of the first matched case.

One or more `WHEN` clauses can be used.

## Examples

The following example shows a simple `CASE` statement usage:

```sql theme={null}
FUNCTION simple_case(a bigint)
  RETURNS varchar
  BEGIN
    CASE a
      WHEN 0 THEN RETURN 'zero';
      WHEN 1 THEN RETURN 'one';
      ELSE RETURN 'more than one or negative';
    END CASE;
    RETURN NULL;
  END
```

Further examples of varying complexity that cover usage of the `CASE` statement
in combination with other statements are available in the [SQL routines examples
documentation](/sql/routines/examples).

## See also

* [routines](/sql/routines/introduction)
* [Conditional expressions using `CASE`](/sql/functions/conditional#case-expression)