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(answer_cnt)/COUNT(DISTINCT question_practice_detail.device_id) as avg_answer_cnt FROM user_profile,question_detail,question_practice_detail WHERE user_profile.device_id=question_practice_detail.device_id AND question_practice_detail.question_id=question_detail.question_id AND university='山东大学' GROUP BY university,difficult_level;
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