DROP FUNCTION [IF EXISTS] function_name

This statement drops the loadable function named function_name. (DROP FUNCTION is also used to drop stored functions; see Section 13.1.29, “DROP PROCEDURE and DROP FUNCTION Statements”.)

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

DROP FUNCTION also removes the function from the Performance Schema user_defined_functions table that provides runtime information about installed loadable functions. See Section 27.12.21.8, “The user_defined_functions Table”.

During the normal startup sequence, the server loads functions 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.

DROP FUNCTION cannot be used to drop a loadable function that is installed automatically by components or plugins rather than by using CREATE FUNCTION. Such a function is also dropped automatically, when the component or plugin that installed it is uninstalled.