题解 | #统计每个学校各难度的用户平均刷题数#

统计每个学校各难度的用户平均刷题数

https://www.nowcoder.com/practice/5400df085a034f88b2e17941ab338ee8

select university,difficult_level,count(dl.question_id)/count(distinct up.device_id) avg_answer_cnt from (select device_id,qpd.question_id question_id,difficult_level from question_practice_detail as qpd join question_detail as qd on qpd.question_id=qd.question_id) dl inner join user_profile as up on dl.device_id=up.device_id group by university,difficult_level

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