题解 | #各用户等级的不同得分表现占比#

select level,score_grade,
round(count(*)/(sum(count(*)) over(partition by level)),3) as ratio
from
(select user_info.uid,level,score,
case when score >= 90 then '优' when score >= 75 then '良'
when score >= 60 then '中' else '差' end as score_grade
from user_info,exam_record
where user_info.uid = exam_record.uid
and score is not null) a
group by level,score_grade
order by level desc,ratio desc