Question

我有一个如下所述的表，并且使用BEFORE INSERT触发器将列的值更新为会话定义的变量。 INSERT集的modified_by_user和created_by_user列均为预期的1。但是，UPDATE不会像我预期的那样将modified_by_user更改为2，而是将其保留为1.如何使用BEFORE UPDATE ON来更新列值？我正在使用MySQL 5.5。感谢

SET @users_id=1;
INSERT INTO notes(notes,record_status_id,date_created) VALUES("hello","active",NOW());
//modified_by_user=1, created_by_user=1, notes="hello"

SET @users_id=2;
UPDATE notes SET notes="goodby" WHERE id=1;
//modified_by_user=1, created_by_user=1, notes="goodby"

CREATE  TABLE IF NOT EXISTS `notes` (
  `id` INT UNSIGNED NOT NULL AUTO_INCREMENT ,
  `notes` TEXT NULL ,
  `record_status_id` VARCHAR(8) NOT NULL ,
  `date_created` DATETIME NOT NULL ,
  `date_modified` TIMESTAMP NOT NULL ,
  `modified_by_user` INT UNSIGNED NULL ,
  `created_by_user` INT UNSIGNED NULL ,
  PRIMARY KEY (`id`) ,
  INDEX `fk_notes_users1_idx` (`modified_by_user` ASC) ,
  INDEX `fk_notes_users2_idx` (`created_by_user` ASC) ,
  INDEX `fk_notes_record_status1_idx` (`record_status_id` ASC) ,
  CONSTRAINT `fk_notes_users10`
    FOREIGN KEY (`modified_by_user` )
    REFERENCES `users` (`id` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `fk_notes_users20`
    FOREIGN KEY (`created_by_user` )
    REFERENCES `users` (`id` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `fk_notes_record_status1`
    FOREIGN KEY (`record_status_id` )
    REFERENCES `record_status` (`id` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;

DELIMITER $$


CREATE TRIGGER tg_notes_ins BEFORE INSERT ON notes FOR EACH ROW
BEGIN
    IF NEW.created_by_user IS NULL OR NEW.created_by_user = '' THEN
        SET NEW.created_by_user = @users_id;
        SET NEW.modified_by_user = @users_id;
    END IF;
END$$



CREATE TRIGGER tg_notes_upd BEFORE UPDATE ON notes FOR EACH ROW
BEGIN
    IF NEW.modified_by_user IS NULL OR NEW.modified_by_user = '' THEN
        SET NEW.modified_by_user = @users_id;
    END IF;
END$$


DELIMITER ;

Answer 1

在UPDATE上，如果查询没有为给定列指定值，则NEW.column不像我原先预期的那样是NULL，但是如果它没有改变则是该列的值（即前一个OLD.column）值）

使用BEFORE UPDATE ON更新列值

1 个答案: