题解 | #统计每个学校的答过题的用户的平均答题数#
统计每个学校的答过题的用户的平均答题数
http://www.nowcoder.com/practice/88aa923a9a674253b861a8fa56bac8e5
select a.university,a.avg_answer_cnt
from
(select u.university,
round(count(q.question_id)/count(distinct q.device_id),1) avg_answer_cnt
from user_profile u
left join question_practice_detail q
on u.device_id=q.device_id
group by u.university)a
where a.avg_answer_cnt>0;
