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 t1.university,t3.difficult_level,count(t3.difficult_level)/count(DISTINCT t1.device_id) from user_profile as t1 inner join question_practice_detail as t2 on t1.device_id = t2.device_id and university = "山东大学" inner join question_detail as t3 on t2.question_id = t3.question_id group by t3.difficult_level
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