mysql - 制作一个 SQL 触发器，如果​​它与已存在的行相似，则不会插入该行

Question

我正在创建一个将在之前发生的触发器，并且该事件在 phpMyAdmin 中为 INSERT。

IF(
    SELECT * FROM packageArchive
    WHERE EXISTS(
                  SELECT * FROM packageArchive WHERE 
                  packageArchive.item = NEW.item
                  AND packageArchive.pack = NEW.pack
                  AND packageArchive.weight = NEW.weight
                  ) THEN
-- Does nothing with this insert / Doesn't insert.

如果您有任何建议，我愿意试一试。

Answer 1

我在 @Juan Carlos Oropeza 和 @RuiDC 和 @Drew 的帮助下解决了这个问题我的解决方案是这样的

IF(
    SELECT * FROM productsArchive WHERE 
    packageArchive.item = NEW.item
    AND packageArchive.pack = NEW.pack
    AND packageArchive.weight = NEW.weight
   ) THEN
signal sqlstate '45000' set message_text = 'My Error Message';
END IF;