题解 | 统计每个用户的平均刷题数
统计每个用户的平均刷题数
https://www.nowcoder.com/practice/f4714f7529404679b7f8909c96299ac4
SELECT
U.university,
QD.difficult_level,
ROUND(COUNT(Q.question_id)/COUNT(DISTINCT(Q.device_id)),4) AS avg_answer_cnt
FROM
user_profile U,
question_practice_detail Q,
question_detail QD
WHERE
U.university= '山东大学' AND
U.device_id = Q.device_id AND
Q.question_id = QD.question_id
GROUP BY
QD.difficult_level
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