MySQL中，sql语句中变量的声明和使用

MySQL中，sql语句中变量的声明和使用

SET @openId='on1234234adfweradf234';
/*删除系统用*/
DELETE FROM `USER` WHERE id IN (SELECT a.`USER_ID` FROM `WEIXIN_INFO` a WHERE a.`OPEN_ID`=@openId);
/*删除微信用户*/
DELETE FROM `WEIXIN_INFO` WHERE `OPEN_ID`=@openId;