MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide
The CREATE FUNCTION statement is
used to create stored functions and user-defined functions (UDFs):
For information about creating stored functions, see Section 13.1.15, “CREATE PROCEDURE and CREATE FUNCTION Statements”.
For information about creating user-defined functions, see Section 13.7.3.1, “CREATE FUNCTION Statement for User-Defined Functions”.