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 university,round(count(d.question_id)/count(distinct u.device_id),4)as avg_answer_cnt from user_profile as u right join question_practice_detail as d on u.device_id=d.device_id group by u.university order by u.university #求问，为什么我用左连接是错的？？？？
