题解 | #浙大不同难度题目的正确率#

select difficult_level ,
    sum(if(qpd.result='right',1,0))/count(qpd.question_id) as correct_rate   //正确率:正确数/总数
from 
    question_practice_detail qpd
    left join question_detail qd on qd.question_id=qpd.question_id
    left join user_profile up on up.device_id=qpd.device_id
where
    up.university='浙江大学'    //需求是浙江大学
group by 
    difficult_level    //按难度分组
order by 
    correct_rate;   //正确率升序排序，asc可以省略