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 qpd.device_id) as avg_answer_cnt from user_profile up join question_practice_detail qpd on up.device_id=qpd.device_id group by university order by university
难点在于平均答题数的计算：题目数/不同的用户数。
