题解 | #月均完成试卷数不小于3的用户爱作答的类别#
月均完成试卷数不小于3的用户爱作答的类别
https://www.nowcoder.com/practice/b1d13efcfa0c4ecea517afbdb9090845
select tag,count(tag) from exam_record er left join examination_info ei on er.exam_id=ei.exam_id
where uid in (
select uid from exam_record
where submit_time is not null
group by uid,date_format(submit_time,'%Y%m')
having sum(if(submit_time is not null,1,0))>=3
)
group by tag
order by count(tag) desc;
老实说我感觉这个题目写的让人很迷惑，很容易想成求月平均完成试卷数大于3啊。。。。
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