题解 | #统计复旦用户8月练题情况#

SELECT
    u.device_id,
    u.university,
    COALESCE(q.question_cnt, 0) AS question_cnt,
    COALESCE(q.right_question_cnt, 0) AS right_question_cnt
FROM
    user_profile AS u
    LEFT OUTER JOIN (
        SELECT
            device_id,
            SUM(
                CASE
                    WHEN date LIKE '2021-08%' THEN 1
                    ELSE 0
                END
            ) AS question_cnt,
            SUM(
                CASE
                    WHEN result = 'right' THEN 1
                    ELSE 0
                END
            ) AS right_question_cnt
        FROM
            question_practice_detail
        WHERE
            date LIKE '2021-08%'
        GROUP BY
            device_id
    ) AS q ON u.device_id = q.device_id
WHERE u.university = '复旦大学';