题解 | #浙大不同难度题目的正确率#简单理解

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