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,convert(count(question_id) / count(distinct u.device_id),decimal(10,4)) from user_profile u inner join
question_practice_detail q on u.device_id = q.device_id
group by u.university order by u.university;
question_practice_detail q on u.device_id = q.device_id
group by u.university order by u.university;