Syntax:
DROP {PROCEDURE | FUNCTION} [IF EXISTS] sp_name

These statements are used to drop a stored routine (a stored procedure
or function). That is, the specified routine is removed from the
server. (DROP FUNCTION is also used to drop loadable functions; see
[HELP DROP FUNCTION loadable function].)

To drop a stored routine, you must have the ALTER ROUTINE privilege for
it. (If the automatic_sp_privileges system variable is enabled, that
privilege and EXECUTE are granted automatically to the routine creator
when the routine is created and dropped from the creator when the
routine is dropped. See
https://dev.mysql.com/doc/refman/5.7/en/stored-routines-privileges.html
.)

The IF EXISTS clause is a MySQL extension. It prevents an error from
occurring if the procedure or function does not exist. A warning is
produced that can be viewed with SHOW WARNINGS.

URL: https://dev.mysql.com/doc/refman/5.7/en/drop-procedure.html

