If we have ALTER ROUTINE privileges then we can alter MySQL stored function with the help of ALTER FUNCTION query. Its syntax is as follows −
Syntax
ALTER FUNCTION function_name [characteristic ...] characteristic: { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } | COMMENT 'string'
Here function_name is the name of the function which we want to alter.
The ALTER FUNCTION statement can change the characteristics, defined above in the syntax, of a stored function. We can specify more than one change in an ALTER FUNCTION statement. But we cannot change the parameters or body of the function with this statement. To illustrate it we are adding comments in the function name ‘factorial’ in the following example −
Example
mysql> ALTER FUNCTION factorial COMMENT 'Can accept fraction values'; Query OK, 0 rows affected (0.00 sec) mysql> Show Create Function factorial\G *************************** 1. row *************************** Function: factorial sql_mode: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION Create Function: CREATE DEFINER=`root`@`localhost` FUNCTION `factorial`(n DECIMAL(3,0)) RETURNS decimal(20,0) DETERMINISTIC COMMENT 'Can accept fraction values' BEGIN DECLARE factorial DECIMAL(20,0) DEFAULT 1; DECLARE counter DECIMAL(3,0); SET counter = n; factorial_loop: REPEAT SET factorial = factorial * counter; SET counter = counter - 1; UNTIL counter = 1 END REPEAT; RETURN factorial; END character_set_client: cp850 collation_connection: cp850_general_ci Database Collation: latin1_swedish_ci 1 row in set (0.00 sec)
From the CREAT FUNCTION query, it is clear that Comment has been added to the definition of function ‘factorial’.