题解 | #统计复旦用户8月练题情况#简单理解
https://www.nowcoder.com/practice/53235096538a456b9220fce120c062b3
SELECT
up.device_id,
up.university,
count( question_id ) AS question_cnt,
( SELECT COUNT(*) FROM question_practice_detail WHERE result = "right" AND device_id = up.device_id ) AS right_question_cnt
FROM
user_profile up
LEFT JOIN question_practice_detail qpd ON up.device_id = qpd.device_id AND MONTH ( qpd.date ) = 8
WHERE
university = "复旦大学"
GROUP BY
up.device_id
up.device_id,
up.university,
count( question_id ) AS question_cnt,
( SELECT COUNT(*) FROM question_practice_detail WHERE result = "right" AND device_id = up.device_id ) AS right_question_cnt
FROM
user_profile up
LEFT JOIN question_practice_detail qpd ON up.device_id = qpd.device_id AND MONTH ( qpd.date ) = 8
WHERE
university = "复旦大学"
GROUP BY
up.device_id
