题解 | #近三个月未完成试卷数为0的用户完成情况#

having语句筛选出完成试卷数和作答试卷数相同的记录，因为这个条件意味着用户没有未完成的试卷

select uid,count(score) as  exam_complete_cnt
from 
(
    select *
    ,date_format(start_time,"%Y%m") as month
    ,dense_rank() over(partition by uid order by date_format(start_time,"%Y%m") desc) as rk 
    from exam_record
) t 
where rk <=3
group by uid
having exam_complete_cnt=count(id) 
order by exam_complete_cnt desc,uid desc