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 u.university , count(q.question_id)/count(DISTINCT q.device_id) from question_practice_detail q inner join
user_profile u where q.device_id =u.device_id group by u.university
