题解 | #统计复旦用户8月练题情况#

select a.device_id,a.university,count(b.device_id) question_cnt,sum(case when b.result='right' then 1 else 0 end) right_question_cnt from (select * from user_profile where university='复旦大学') a left join (select * from question_practice_detail where MONTH(date)=8) b on a.device_id=b.device_id group by a.device_id order by a.device_id