题解 | #浙大不同难度题目的正确率#

SELECT difficult_level,SUM(IF(qp.result='right',1,0))/COUNT(qp.question_id) correct_rate
FROM user_profile up 
LEFT JOIN question_practice_detail qp 
ON up.device_id = qp.device_id
JOIN question_detail qd ON qp.`question_id`=qd.`question_id` 
WHERE university='浙江大学' GROUP BY difficult_level 
order by correct_rate asc;