题解 | #浙大不同难度题目的正确率#

select q1.difficult_level,count(case when result='right'then 1 else null end)/count(result) as correct_rate from question_detail q1 join question_practice_detail q2 on q1.question_id=q2.question_id join user_profile u1 on u1.device_id=q2.device_id where university='浙江大学' group by q1.difficult_level order by correct_rate