题解 | #近三个月未完成试卷数为0的用户完成情况#

select uid,count(score) 'exam_complete_cnt'
from (select uid,score,dense_rank() over(partition by uid order by date_format(start_time,'%Y%m' ) desc) 'rk' from exam_record) s
where rk<=3
group by uid
having count(uid)=count(score)
order by exam_complete_cnt desc,uid desc;

dense_rank()连续排序，相等数据序号相等

无未完成试卷，则每次作答都有成绩，count(uid)=count(score)