On update trigger in MySQL - php

Question

CREATE TABLE IF NOT EXISTS `comenzi` (
`idcomanda` int(11) NOT NULL AUTO_INCREMENT,
`iduser` int(11) DEFAULT NULL,
`idprodus` int(11) DEFAULT NULL,
`numepiesa` varchar(50) COLLATE utf8_unicode_ci DEFAULT NULL,
`pretunit` int(11) DEFAULT NULL,
`cantitate` int(11) DEFAULT NULL,
`pretftva` int(11) DEFAULT NULL,
`valtva` int(11) DEFAULT NULL,
`total` int(11) DEFAULT NULL,
`nrfactura` int(11) unsigned zerofill DEFAULT NULL,
`achitat` tinyint(4) DEFAULT NULL,
`dataachitat` date DEFAULT NULL,
PRIMARY KEY (`idcomanda`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
Hey Guys,I have the table structure mentioned above and I never did triggers in MySQL, could you help me out with this one please.
I need to update the "dataachitat"column with the currentdate everytime a row has the "achitat" value set to 1
Ex. Let's say that the first item is affected by an update script and the achitat value is set to 1, i need the "dataachitat" column of that row to be automatically set to currentdate.
Please help me out
Cheers !

Answer 1

A BEFORE UPDATE trigger to perform the specified action would look something like this:
DELIMITER $$
CREATE TRIGGER trg_comenzi_bu
BEFORE UPDATE ON comenzi
FOR EACH ROW
BEGIN
IF NEW.achitat = 1 THEN
SET NEW.dataachitat = DATE(NOW());
END IF;
END$$
DELIMITER ;
(This is desk checked only; there could be issues with the order of the keywords; the BEFORE UPDATE might come after ON comenzi, et al.)
NOTE: The BEFORE UPDATE trigger will only be "fired" when an UPDATE statement affects a row in the table, it won't be fired when a row is inserted to the table. You'd need an equivalent BEFORE INSERT trigger to do the same thing on an INSERT.
NOTE: The IF statement in the trigger body checks if the value of the achitat column is 1; it doesn't check if the previous (OLD) value was something other than 1. That is, the IF will evaluate to TRUE whether the achitat was changed to a 1, or if it was already a 1.
If you only want the SET action to be performed if the achitat column is changed to 1 from some other value, you could do something like this:
IF (NEW.achitat = 1 AND (OLD.achitat <> 1 OR OLD.achitat IS NULL)) THEN