UNION排序 | #每个题目和每份试卷被作答的人数和次数#

select *
from
(select exam_id tid, count(distinct uid) uv, count(1) pv
from exam_record
group by exam_id
order by uv desc, pv desc) t1
union
select *
from
(select question_id tid, count(distinct uid) uv, count(1) pv
from practice_record
group by question_id
order by uv desc, pv desc) t2;

两个表排序后联合，需要额外添加一层select *。