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
使用left join方式，注意月份要在on条件下
select a.device_id,a.university,count(b.question_id) as question_cnt,sum(if(b.result='right',1,0)) as right_question_cnt from user_profile as a left join question_practice_detail as b on a.device_id=b.device_id and month(b.date)=8 where a.university='复旦大学' group by a.device_id,a.university
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