题解 | #每个题目和每份试卷被作答的人数和次数#

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