题解 | #月均完成试卷数不小于3的用户爱作答的类别#
月均完成试卷数不小于3的用户爱作答的类别
http://www.nowcoder.com/practice/b1d13efcfa0c4ecea517afbdb9090845
select e2.tag , count(tag) as tag_cnt
from exam_record e1 left join examination_info e2 using(exam_id)
where e1.uid in
(select e1.uid
from exam_record e1
where e1.submit_time is not NULL
group by e1.uid, DATE_FORMAT(submit_time, "%Y%m")
having count(e1.submit_time) > 2
)
group by e2.tag
order by tag_cnt desc;