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 as university, count(q.question_id)/count(distinct q.device_id) as avg_answer_cnt FROM question_practice_detail as q INNER JOIN user_profile as u ON q.device_id = u.device_id GROUP BY u.university;