Question

I would like to know if it’s possible to pass a parameter to a mysql stored procedure and use this parameter as the unit parameter of the DATE_SUB function. It seems that the unit parameter is a reserved word so I don’t know if there’s a type for unit.

Exemple of what I’m trying to do :

DELIMITER $$

DROP PROCEDURE IF EXISTS `test` $$
CREATE DEFINER=`root`@`%` PROCEDURE `test`(param1 unit)
BEGIN

select DATE_SUB(now(), INTERVAL 1 param1);

END $$

DELIMITER ;

UPDATE 1
I tried with a prepare statement, I’m able to create the stored proc.

DELIMITER $$

DROP PROCEDURE IF EXISTS `test` $$
CREATE DEFINER=`root`@`%` PROCEDURE `test`(param1 varchar(10))
BEGIN


PREPARE stmt FROM 'SELECT DATE_SUB(now(), INTERVAL 1 ?)';
EXECUTE stmt USING @param1;


END $$

DELIMITER ;

When I executed it :
CALL test(‘WEEK’);
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘?)’ at line 1

Answer 1

What you are trying to do is not possible in a stored procedure, with or without a prepared statement.

You could do something similar like this:

DELIMITER $$

DROP PROCEDURE IF EXISTS test_proc $$
CREATE PROCEDURE  test_proc(param1 varchar(20))
BEGIN

  CASE UPPER(param1)
    WHEN 'MICROSECOND' THEN select DATE_SUB(now(), INTERVAL 1 MICROSECOND); 
    WHEN 'SECOND' THEN select DATE_SUB(now(), INTERVAL 1 SECOND);
    WHEN 'MINUTE' THEN select DATE_SUB(now(), INTERVAL 1 MINUTE);
    WHEN 'HOUR' THEN select DATE_SUB(now(), INTERVAL 1 HOUR);
    WHEN 'DAY' THEN select DATE_SUB(now(), INTERVAL 1 DAY);
    WHEN 'WEEK' THEN select DATE_SUB(now(), INTERVAL 1 WEEK);
    WHEN 'MONTH' THEN select DATE_SUB(now(), INTERVAL 1 MONTH);
    WHEN 'QUARTER' THEN select DATE_SUB(now(), INTERVAL 1 QUARTER);
    WHEN 'YEAR' THEN select DATE_SUB(now(), INTERVAL 1 YEAR);
    ELSE select 'UNEXPECTED UNIT';
  END CASE;

END $$

DELIMITER ;