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 tid,count(distinct uid) uv,count(uid) 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(uid) pv
from practice_record
group by question_id
order by uv desc,pv desc) t2;

直接union会导致无法按照试卷和题目的顺序，所以先分别排序后再union