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 specified name and type from the provided library file. The library file must be located in a trusted plugin_dir directory. Upon successful installation, the function becomes available for use in all subsequent queries received by the server. 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 |
+------+--------+---------+-----------+

DROP FUNCTION udf_name

DROP FUNCTION statement uninstalls a user-defined function UDF with the specified name. Upon successful removal, the function will no longer be available for use in subsequent queries. However, ongoing concurrent queries will not be affected, and if necessary, the library unloading will be delayed until those queries are completed. Example:

mysql> DROP FUNCTION avgmva;
Query OK, 0 rows affected (0.00 sec)