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,
ROUND(COUNT(*) / COUNT(DISTINCT u.device_id), 4) AS avg_answer_cnt
FROM question_practice_detail p,
user_profile u,
question_detail d
WHERE u.device_id = p.device_id
AND p.question_id = d.question_id
GROUP BY university, difficult_level
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