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 distinct university, round(count(question_id) / count(distinct u.device_id), 4) as avg_answer_cnt from user_profile u left join question_practice_detail p on u.device_id = p.device_id where question_id is not null group by university order by university asc
1.题目中有“答过题”的条件，4321是没有答过题的，要排除。
2.注意去重
3.注意保留4位小数
4.排序