题解 | #统计复旦用户8月练题情况#
统计复旦用户8月练题情况
https://www.nowcoder.com/practice/53235096538a456b9220fce120c062b3
select up.device_id ,university ,count(qpd.result) question_cnt ,sum(if(qpd.result='right',1,0)) from user_profile up left join question_practice_detail qpd on up.device_id=qpd.device_id and month(date)='8' where up.university='复旦大学' group by up.device_id
and month(date)='8'放到from里，而不是where里
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