题解 | #统计每个用户的平均刷题数#
统计每个用户的平均刷题数
https://www.nowcoder.com/practice/f4714f7529404679b7f8909c96299ac4
select university,difficult_level,count(qpd.question_id)/count(distinct qpd.device_id) from user_profile as up,question_practice_detail as qpd,question_detail as qd where up.device_id=qpd.device_id and qpd.question_id=qd.question_id group by university,difficult_level having university='山东大学';
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