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
http://www.nowcoder.com/practice/88aa923a9a674253b861a8fa56bac8e5
SELECT university,COUNT(question_id)/COUNT(DISTINCT u.device_id) AS avg_answer_cnt
FROM user_profile u
INNER JOIN question_practice_detail qpd
ON u.device_id = qpd.device_id
GROUP BY university;
FROM user_profile u
INNER JOIN question_practice_detail qpd
ON u.device_id = qpd.device_id
GROUP BY university;
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