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
http://www.nowcoder.com/practice/53235096538a456b9220fce120c062b3
if（*判断条件*,*满足返回*,*不满足返回*）
count()计数，无论数值多少，计数+1
sum()总数，计算数值总和
select t1.device_id, university, count(date)qusetion_cnt, sum(if(t2.result = 'right',1,0))right_question_cnt from user_profile t1 left join question_practice_detail t2 on t1.device_id = t2.device_id and date like '2021-08%' where university = '复旦大学' group by t1.device_id
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