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
https://www.nowcoder.com/practice/88aa923a9a674253b861a8fa56bac8e5
select B.university, count(A.question_id)/count(distinct B.device_id) as avg_answer_cnt from question_practice_detail A left join user_profile B on A.device_id = B.device_id group by B.university