phpmyadmin添加一个触发器，防止某个字段被恶意篡改

BEGIN
	if (new.qrcode_url != '') then
		set new.qrcode_url = old.qrcode_url;
	end if;
END

BEGIN if (new.qrcode_url != '') then set new.qrcode_url = old.qrcode_url; end if; END