两个sql查询使用union之后排序失效的解决方法

(SELECT*FROM(SELECTa.id,a.userId,a.infoId,a.isRead,a.infoType,b.title,b.createTimeFROMc_user_info aLEFT JOIN c_info b ON a.infoId = b.idWHERE1 = 1AND isRead = '0'AND userId = '1'ORDER BYb.createTime DESC) AS activity1)UNION (SELECT*FROM(SELECTa.id,a.userId,a.infoId,a.isRead,a.infoType,b.title,b.createTimeFROMc_user_info aLEFT JOIN c_info b ON a.infoId = b.idWHERE1 = 1AND isRead = '1'AND userId = '1'ORDER BYb.createTime DESC) AS activity2);

解决方法：在每一个sql语句都是使用select  * from (sql语句) as  activity  ，将activity  进行union操作。