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(QPD.question_id) AS correct_rate
FROM question_practice_detail AS QPD
INNER JOIN user_profile AS UP
ON QPD.device_id=UP.device_id
INNER JOIN question_detail AS QD
ON QPD.question_id=QD.question_id
WHERE UP.university='浙江大学'
GROUP BY QD.difficult_level
ORDER BY correct_rate;