MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
The mysql.func system table shows which
loadable functions have been registered using
CREATE FUNCTION:
SELECT * FROM mysql.func;
The func table has these columns:
name
The function name as referred to in SQL statements.
ret
The function return value type. Permitted values are 0
(STRING), 1 (REAL), 2
(INTEGER), 3 (ROW), or 4
(DECIMAL).
dl
The name of the function library file containing the
executable function code. The file is located in the directory
named by the plugin_dir
system variable.
type
The function type, either function (scalar)
or aggregate.