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, ROUND(count(b.question_id)/count(distinct(b.device_id)),4) as avg_answer_cnt from user_profile as a right join question_practice_detail as b on a.device_id = b.device_id group by a.university;
