题解 | #近三个月未完成试卷数为0的用户完成情况#

1. 近三个月，rank<=3，where
2. 没有试卷是未完成的状态：分组后筛选，开始数=得分次数 having count

select
uid,
count(start_time) as exam_complete_cnt
from(
select 
  *,
  dense_rank() over(partition by uid order by date_format(start_time,"%Y%m") desc) as ranking
from exam_record
) t1
where ranking <= 3
group by uid
having count(start_time) = count(score) -- 开始数=得分次数
order by exam_complete_cnt desc,uid desc