题解 | #浙大不同难度题目的正确率#

SELECT
    qd.difficult_level,
    (SUM(IF (qpd.result = 'right', 1, 0)) / COUNT(*)) AS correct_rate
FROM
    user_profile up
    INNER JOIN question_practice_detail qpd ON up.device_id = qpd.device_id
    INNER JOIN question_detail qd ON qpd.question_id = qd.question_id
WHERE
    university = '浙江大学'
GROUP BY
    qd.difficult_level
ORDER BY
    correct_rate ASC