SHOW LOCALES was introduced as part of the Information Schema plugin extension.

SHOW LOCALES is used to return locales information as part of the Locales
plugin. While the information_schema.LOCALES table has 8 columns, the SHOW
LOCALES statement will only display 4 of them:

Example
-------

SHOW LOCALES;
+-----+-------+-------------------------------------+------------------------+
| Id  | Name  | Description                         | Error_Message_Language |
+-----+-------+-------------------------------------+------------------------+
|   0 | en_US | English - United States             | english                |
|   1 | en_GB | English - United Kingdom            | english                |
|   2 | ja_JP | Japanese - Japan                    | japanese               |
|   3 | sv_SE | Swedish - Sweden                    | swedish                |
...

URL: https://mariadb.com/kb/en/show-locales/