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(*)/count( distinct a.device_id)
as avg_answer_cnt from user_profile as a left join question_practice_detail as b
on a.device_id=b.device_id left join question_detail as c on b.question_id=c.question_id
group by university,difficult_level having difficult_level is not null;
as avg_answer_cnt from user_profile as a left join question_practice_detail as b
on a.device_id=b.device_id left join question_detail as c on b.question_id=c.question_id
group by university,difficult_level having difficult_level is not null;
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