CREATE FUNCTION udf_name
    RETURNS {INT | INTEGER | BIGINT | FLOAT | STRING}
    SONAME 'udf_lib_file'

CREATE FUNCTION statement installs a user-defined function UDF with the given name and type from the given library file. The library file must reside in a trusted plugin_dir directory. On success, the function is available for use in all subsequent queries that the server receives. Example:

mysql> CREATE FUNCTION avgmva RETURNS INTEGER SONAME 'udfexample.dll';
Query OK, 0 rows affected (0.03 sec)

mysql> SELECT *, AVGMVA(tag) AS q from test1;
+------+--------+---------+-----------+
| id   | weight | tag     | q         |
+------+--------+---------+-----------+
|    1 |      1 | 1,3,5,7 | 4.000000  |
|    2 |      1 | 2,4,6   | 4.000000  |
|    3 |      1 | 15      | 15.000000 |
|    4 |      1 | 7,40    | 23.500000 |
+------+--------+---------+-----------+