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 u.university, qd.difficult_level,
COUNT(qp.question_id)/COUNT(DISTINCT qp.device_id) AS avg_answer_cnt
FROM user_profile u
JOIN question_practice_detail qp
USING(device_id)
JOIN question_detail qd
USING(question_id)
GROUP BY u.university, qd.difficult_level
HAVING u.university='山东大学'
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