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 university,difficult_level,count(b.question_id)/count(distinct a.device_id) as avg__answer_cnt from user_profile a join question_practice_detail b on b.device_id = a.device_id join question_detail c on c.question_id = b.question_id group by university,difficult_level having university = '山东大学';
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