Question

I’m trying to write a trigger to solve innodb auto_increment problem. I want to make orderID is auto_increment however innodb does not allow me. Here is ORDER table

CREATE TABLE IF NOT EXISTS `ORDER` (
  `placeID` INT UNSIGNED NOT NULL,
  `orderID` INT UNSIGNED NOT NULL,
  `userID` INT UNSIGNED NOT NULL ,
  `tableNum` SMALLINT NOT NULL,
  `orderStatus` TINYINT NOT NULL,
  `orderDate` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`placeID`,`orderID`),
  FOREIGN KEY (`userID`) REFERENCES `USER` (`userID`),
  FOREIGN KEY (`placeID`) REFERENCES `PLACE` (`placeID`))
ENGINE=InnoDB;

Here is the trigger

delimiter $$
DROP TRIGGER /*!50032 IF EXISTS */ `ORDER_TRIGGER` $$
CREATE TRIGGER `ORDER_TRIGGER` BEFORE INSERT ON `ORDER`
FOR EACH ROW
BEGIN
        DECLARE orderID INT UNSIGNED;
    SELECT MAX(`orderID`) INTO orderID FROM `ORDER` WHERE `placeID` = NEW.placeID;
        IF orderID IS NULL THEN
            orderID = 1;
        END IF;
    SET NEW.orderID = orderID+1;
END;
$$
delimiter;

When I execute this script I get this error.

#1064 - 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 '= 1;
        END IF;
    SET NEW.orderID = orderID+1;
END' at line 7 

Can anybody help me? I looked at google but I can’t find accurate solution.

Answer 1

I found my mistake. This is right code.

delimiter $$
DROP TRIGGER /*!50032 IF EXISTS */ `ORDER_TRIGGER` $$
CREATE TRIGGER `ORDER_TRIGGER` BEFORE INSERT ON `ORDER`
FOR EACH ROW
BEGIN
        DECLARE orderID INT UNSIGNED;
        SELECT MAX(`ORDER`.`orderID`) AS ID INTO orderID FROM `ORDER` WHERE `ORDER`.`placeID` = NEW.placeID;
        IF orderID IS NULL THEN
            SET orderID = 0;
        END IF;
    SET NEW.orderID = orderID+1;
END;
$$