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(qpd.device_id) / count(distinct qpd.device_id) ,4) as avg_answer_cnt from question_practice_detail as qpd inner join user_profile as up on qpd.device_id = up.device_id Group by university order by university;
来自两个表from ... inner join...
两个表中的成分相等
on 表1.列=表2.列
