> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/reference/sql-structure/operators/comparison-operators/is-not.md).

# IS NOT

Test a value against TRUE, FALSE, or UNKNOWN and negate the result. IS NOT always returns 1 or 0, never NULL.

## Syntax

```bnf
IS NOT boolean_value
```

## Description

Tests a value against a boolean value, where `boolean_value` can be `TRUE`, `FALSE`, or `UNKNOWN`.

`IS NOT` always returns `1` or `0`, never `NULL`. When the value is `NULL`, `IS NOT TRUE` and `IS NOT FALSE` both return `1`. To test for a non-`NULL` value directly, use [IS NOT NULL](/docs/server/reference/sql-structure/operators/comparison-operators/is-not-null.md).

## Examples

```sql
SELECT 1 IS NOT UNKNOWN, 0 IS NOT UNKNOWN, NULL IS NOT UNKNOWN;
+------------------+------------------+---------------------+
| 1 IS NOT UNKNOWN | 0 IS NOT UNKNOWN | NULL IS NOT UNKNOWN |
+------------------+------------------+---------------------+
|                1 |                1 |                   0 |
+------------------+------------------+---------------------+
```

```sql
SELECT NULL IS NOT TRUE, NULL IS NOT FALSE;
+------------------+-------------------+
| NULL IS NOT TRUE | NULL IS NOT FALSE |
+------------------+-------------------+
|                1 |                 1 |
+------------------+-------------------+
```

## See Also

* [IS](/docs/server/reference/sql-structure/operators/comparison-operators/is.md)
* [IS NOT NULL](/docs/server/reference/sql-structure/operators/comparison-operators/is-not-null.md)
* [Operator Precedence](/docs/server/reference/sql-structure/operators/operator-precedence.md)

<sub>*This page is licensed: GPLv2, originally from*</sub> [<sub>*fill\_help\_tables.sql*</sub>](https://github.com/MariaDB/server/blob/main/scripts/fill_help_tables.sql)

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