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
	user_profile u
	INNER JOIN question_practice_detail q ON u.device_id = q.device_id
	INNER JOIN question_detail d ON q.question_id = d.question_id 
GROUP BY
	university,
	difficult_level

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