DROP FUNCTION [IF EXISTS] function_name

This statement drops the user-defined function (UDF) named function_name. (DROP FUNCTION is also used to drop stored functions; see Section 13.1.27, “DROP PROCEDURE and DROP FUNCTION Statements”.)

DROP FUNCTION is the complement of CREATE FUNCTION. It requires the DELETE privilege for the mysql system database because it removes the row from the mysql.func system table that registers the function.

During the normal startup sequence, the server loads UDFs registered in the mysql.func table. Because DROP FUNCTION removes the mysql.func row for the dropped function, the server does not load the function during subsequent restarts.