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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