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(qpd.question_id) / COUNT(distinct qpd.device_id) , 4) AS avg_answer_cnt
FROM user_profile AS up
INNER JOIN question_practice_detail AS qpd ON up.device_id = qpd.device_id
INNER JOIN question_detail AS qd ON qpd.question_id = qd.question_id
GROUP BY university, difficult_level
ORDER BY university
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