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