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 up.university,
qd.difficult_level,
round(count(qpd.question_id)/count(distinct qpd.device_id),4) AS avg_answer_cnt
FROM question_practice_detail qpd
LEFT JOIN user_profile up USING(device_id)
LEFT JOIN question_detail qd USING(question_id)
GROUP BY university,difficult_level
或者
SELECT up.university,
qd.difficult_level,
round(count(qpd.question_id)/count(distinct qpd.device_id),4) AS avg_answer_cnt
FROM question_practice_detail qpd,
user_profile up,
question_detail qd
WHERE qpd.device_id = up.device_id
and qpd.question_id = qd.question_id
GROUP BY university,difficult_level
