MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
The CREATE FUNCTION statement is
used to create stored functions and loadable functions:
For information about creating stored functions, see Section 13.1.16, “CREATE PROCEDURE and CREATE FUNCTION Statements”.
For information about creating loadable functions, see Section 13.7.3.1, “CREATE FUNCTION Statement for Loadable Functions”.