題解 | #浙大不同難度題目的正確率#
浙大不同難度題目的正確率
http://www.fangfengwang8.cn/practice/d8a4f7b1ded04948b5435a45f03ead8c
select qd.difficult_level, #正確率是答正確的題/總題數(shù) sum(if(result='right',1,0))/count(qpd.question_id) as correct_rate from user_profile as up inner join question_practice_detail as qpd on up.device_id = qpd.device_id and up.university = '浙江大學(xué)' inner join question_detail as qd on qpd.question_id = qd.question_id #基本的準(zhǔn)備已做好,接下來(lái)開(kāi)始解題 group by qd.difficult_level order by correct_rate asc
大部分思路都對(duì)上了。我發(fā)現(xiàn)自己join的概念還是不清晰,時(shí)常就用錯(cuò)了