题解 | #浙大不同难度题目的正确率#

select 
    t2.difficult_level,
    round(sum(case when result = 'right' then 1 else 0 end )/count(*),4) correct_rate
from 
    question_practice_detail t1
left join   
    question_detail t2
on 
    t1.question_id = t2.question_id
where 
    t1.device_id in (select device_id from user_profile where university = '浙江大学')
group by
    t2.difficult_level
order by
    correct_rate