题解 | #统计复旦用户8月练题情况#

SELECT
    u.device_id,
    u.university,
    COUNT(q.question_id) AS question_cnt,
    SUM(CASE WHEN result = 'right' THEN 1
        ELSE 0 END) AS right_question_cnt
FROM user_profile u
LEFT JOIN question_practice_detail q
on u.device_id = q.device_id
WHERE university = '复旦大学' AND (MONTH(date) = 8 or MONTH(date) IS NULL)
GROUP BY device_id;