最没有意义 | #月均完成试卷数不小于3的用户爱作答的类别#

select tag, count(1) tag_cnt
from
(select uid, count(score) / count(distinct date_format(start_time, '%Y%m')) c
from exam_record
where score is not null
group by uid) t
left join exam_record r
on t.uid = r.uid
left join examination_info i
on r.exam_id = i.exam_id
where c >= 3
group by tag order by tag_cnt desc;

出题人疑似体育老师代课。