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 up.university,(count(qpd.result)/count(distinct qpd.device_id)) as avg_answer_cnt from user_profile as up join question_practice_detail as qpd on up.device_id = qpd.device_id group by up.university 分组:group by,连接 join on,device_id 去重 disctinct