题解 | #浙大不同难度题目的正确率#

select qd.difficult_level,(sum(if(q.result='right',1,0)))/(count(*)) as correct_rate from user_profile u inner join question_practice_detail q on u.device_id=q.device_id left join question_detail qd on q.question_id=qd.question_id where u.university='浙江大学' group by qd.difficult_level order by correct_rate