select * from (SELECT exam_id tid,count(DISTINCT uid) uv,count(uid) pv from exam_record group by exam_id order by uv desc,pv desc)a UNION ALL ---用union all union all :不去重,不排序,数据原始状态拼接 union:去重然后从小到大排序 SELECT * FROM (SELECT question_id tid,count(DISTINCT uid) uv,count(uid) pv from practice_record GRO...