MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide
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 13.1.26, “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.
To upgrade the shared library associated with a UDF, issue a
DROP
FUNCTION
statement, upgrade the shared library, and
then issue a
CREATE
FUNCTION
statement. If you upgrade the shared
library first and then use
DROP
FUNCTION
, the server may unexpectedly shut down.