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(b.question_id)/count(distinct b.device_id)) as avg_answer_cnt from user_profile a join question_practice_detail b on a.device_id = b.device_id join question_detail c on b.question_id = c.question_id group by university,difficult_level

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