题解 | #每个题目和每份试卷被作答的人数和次数#

select * from
(select exam_id             as tid,
        count(distinct uid) as uv,
        count(uid)          as pv
 from exam_record
 group by exam_id
 order by uv desc, pv desc)a
union all
select * from
(
select
    question_id as tid,
    count(distinct uid) as uv,
    count(uid) as pv
from practice_record
group by question_id
order by uv desc ,pv desc)b