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, round(count(b.question_id)/count(distinct b.device_id),4) as avg_answer_cnt from user_profile a inner join question_practice_detail b inner join question_detail c on a.device_id= b.device_id and b.question_id= c.question_id group by university,difficult_level
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