> 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/sql-language-structure/sql-language-structure-boolean-literals.md).

# Boolean Literals

In MariaDB, `FALSE` is a synonym of `0` and `TRUE` is a synonym of `1`. These constants are case insensitive, so `TRUE`, `True`, and `true` are equivalent.

These terms are not synonyms of `0` and `1` when used with the [IS](/docs/server/reference/sql-structure/operators/comparison-operators/is.md) operator. So, for example, `10 IS TRUE` returns `1`, while `10 = TRUE` returns `0` (because 1 != 10).

The `IS` operator accepts a third constant exists: `UNKNOWN`. It is always a synonym of [NULL](/docs/server/reference/data-types/null-values.md).

`TRUE` and `FALSE` are [reserved words](/docs/server/reference/sql-structure/sql-language-structure/reserved-words.md), while `UNKNOWN` is not.

## See Also

* [BOOLEAN](/docs/server/reference/data-types/numeric-data-types/boolean.md) type

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