题解 | #统计每个学校的答过题的用户的平均答题数#
统计每个学校的答过题的用户的平均答题数
https://www.nowcoder.com/practice/88aa923a9a674253b861a8fa56bac8e5
SELECT university,
ROUND(COUNT(question_id)/COUNT(distinct t1.device_id),4) AS avg_answer_cnt
FROM question_practice_detail t1
LEFT JOIN user_profile t2
ON t1.device_id = t2.device_id
GROUP BY university
ORDER BY university
某学校用户平均答题数量=该学校用户答题总次数 / 答过题的不同用户个数
COUNT(...)/COUNT(distinct ...)
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