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
t1.university,
t3.difficult_level,
ROUND(COUNT(t2.question_id)/COUNT(DISTINCT(t2.device_id)),4) AS avg_answer_cnt
FROM user_profile AS t1
JOIN question_practice_detail AS t2 ON t1.device_id=t2.device_id
JOIN question_detail AS t3 ON t2.question_id=t3.question_id
GROUP BY t1.university,t3.difficult_level;
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