MySQL触发器中IF条件判断问题

前几天修改了一张回答表的触发器，结果保存草稿的时候报错：Data truncation: Truncated incorrect datetime value: ''，经排查是触发器中一条判断的问题，我们来看原来的语句：
IF CONCAT(new.delete_flag,new.status)!=CONCAT(old.delete_flag,old.status) AND new.delete_flag=0 AND new.status=0 AND IFNULL(new.publish_time,'')!='' AND new.publish_time>DATE_ADD(NOW(),INTERVAL -30 DAY) THEN
    INSERT IGNORE INTO kid_follow_feed(receiver,operator,type,content_type,content_id,time) VALUES(new.user_id,new.user_id,3,3,new.id,new.publish_time);
    SET v_ret = redis_command_v2('LPUSH', 'mq:CalcFollowFeed', CONCAT(json_object('oper',new.user_id,'type',3,'contentType',3,'contentId',new.id)));
END IF;

原来的语句中先判断状态是否有变化，如果没有变化，再判断是否发布状态并且有发布时间，同时发布时间要在30天之内，结果这条语句就报错了，原因是保存草稿的时候发布时间是空字符串，修改成这样就没问题了：
IF new.delete_flag=0 AND new.status=0 AND IFNULL(new.publish_time,'')!='' THEN
    IF CONCAT(new.delete_flag,new.status)!=CONCAT(old.delete_flag,old.status) AND new.publish_time>DATE_ADD(NOW(),INTERVAL -30 DAY) THEN
      INSERT IGNORE INTO kid_follow_feed(receiver,operator,type,content_type,content_id,time) VALUES(new.user_id,new.user_id,3,3,new.id,new.publish_time);
      SET v_ret = redis_command_v2('LPUSH', 'mq:CalcFollowFeed', CONCAT(json_object('oper',new.user_id,'type',3,'contentType',3,'contentId',new.id)));
    END IF;
  END IF;