题解 | 浙大不同难度题目的正确率

# 浙江大学 不同难度 正确率 升序
select 
    difficult_level,
   sum(if(result = "right",1,0))/count(result) correct_rate
from user_profile up 
left join question_practice_detail qp on up.device_id = qp.device_id
left join question_detail qd on qp.question_id = qd.question_id
where up.university = "浙江大学" and result is not null
group by difficult_level
order by correct_rate;