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, count(question_id)/count(distinct user_profile.device_id) as avg_answer_cnt from user_profile inner join question_practice_detail on question_practice_detail.device_id=user_profile.device_id group by university
inner join question_practice_detail 合并连个表的时候会自动去除合并后每行中包括0的行
虽然但是 总有分开的那一天