题解 | #浙大不同难度题目的正确率#

select qd.difficult_level,avg(if(qpd.result='right', 1, 0)) as correct_rate 
from user_profile as up
inner join question_practice_detail as qpd
    on up.device_id = qpd.device_id
inner join question_detail as qd
    on qd.question_id = qpd.question_id
where university ='浙江大学'
group by difficult_level
order by correct_rate asc;

这一题 avg(if(qpd.result='right', 1, 0)) ascorrect_rate

#    sum(if(qpd.result='right', 1, 0)) / count(qpd.question_id) ascorrect_rate

#    count(if(qpd.result='right', 1, null)) / count(qpd.question_id) ascorrect_rate

不同难题正确率的三种写法