题解 | #统计复旦用户8月练题情况#

SELECT
    user_profile.device_id,
    university,
    SUM(IF(MONTH(date) = 8,1,0)) AS question_cnt,
    SUM(IF(result = 'right' AND MONTH(date) = 8,1,0)) AS right_question_cnt
FROM
    user_profile LEFT JOIN question_practice_detail 
    ON  user_profile.device_id = question_practice_detail.device_id
WHERE
    user_profile.university = '复旦大学' 
GROUP BY
    device_id