# UNCOMPRESS

## Syntax

```sql
UNCOMPRESS(string_to_uncompress)
```

## Description

Uncompresses a string compressed by the [COMPRESS()](https://mariadb.com/docs/server/reference/sql-functions/secondary-functions/encryption-hashing-and-compression-functions/compress) function. If the argument is not a compressed value, the result is `NULL`. This function requires MariaDB to have been compiled with a compression library such as zlib. Otherwise, the return value is always `NULL`. The [have\_compress](https://mariadb.com/docs/server/server-management/variables-and-modes/server-system-variables#have_compress) server system variable indicates whether a compression library is present.

## Examples

```sql
SELECT UNCOMPRESS(COMPRESS('a string'));
+----------------------------------+
| UNCOMPRESS(COMPRESS('a string')) |
+----------------------------------+
| a string                         |
+----------------------------------+

SELECT UNCOMPRESS('a string');
+------------------------+
| UNCOMPRESS('a string') |
+------------------------+
| NULL                   |
+------------------------+
```

<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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