Syntax
------

DROP FUNCTION [IF EXISTS] function_name

Description
-----------

This statement drops the user-defined function (UDF) named function_name.

To drop a function, you must have the DELETE privilege for the mysql database.
This is because DROP FUNCTION removes the row from the mysql.func system table
that records the function's name, type and shared library name.

For dropping a stored function, see DROP FUNCTION.

Upgrading a UDF
---------------

To upgrade the UDF's shared library, first run a DROP FUNCTION statement, then
upgrade the shared library and finally run the CREATE FUNCTION statement. If
you upgrade without following this process, you may crash the server.

Examples
--------

DROP FUNCTION jsoncontains_path;

IF EXISTS:

DROP FUNCTION jsoncontains_path;
ERROR 1305 (42000): FUNCTION test.jsoncontains_path does not exist

DROP FUNCTION IF EXISTS jsoncontains_path;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+------------------------------------------------+
| Level | Code | Message                                        |
+-------+------+------------------------------------------------+
| Note  | 1305 | FUNCTION test.jsoncontains_path does not exist |
+-------+------+------------------------------------------------+

URL: https://mariadb.com/kb/en/drop-function-udf/