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 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
ON u.device_id=qp.device_id
JOIN question_detail qd
ON qp.question_id=qd.question_id
GROUP BY u.university, qd.difficult_level
