Syntax
------ 
DROP FUNCTION [IF EXISTS] f_name
 
Description
----------- 
The DROP FUNCTION statement is used to drop a stored
function or a user-defined function (UDF). That is, the
specified routine is removed from the server, along with all
privileges specific to the function. You must have the ALTER
ROUTINE privilege for the routine in order to drop it. If
the automatic_sp_privileges server system variable is set,
both the ALTER ROUTINE and EXECUTE privileges are granted
automatically to the routine creator - see Stored Routine
Privileges.
 
IF EXISTS
 
The IF EXISTS clause is a MySQL/MariaDB extension. It
prevents an error from occurring if the function does not
exist. A
NOTE is produced that can be viewed with SHOW WARNINGS.
 
For dropping a user-defined functions (UDF), see DROP
FUNCTION UDF.
 
Examples
-------- 
DROP FUNCTION hello;
 
Query OK, 0 rows affected (0.042 sec)
 
DROP FUNCTION hello;
 
ERROR 1305 (42000): FUNCTION test.hello does not exist
 
DROP FUNCTION IF EXISTS hello;
 
Query OK, 0 rows affected, 1 warning (0.000 sec)
 
SHOW WARNINGS;
 
+-------+------+------------------------------------+
| Level | Code | Message |
+-------+------+------------------------------------+
| Note | 1305 | FUNCTION test.hello does not exist |
+-------+------+------------------------------------+
 


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