--分组排序

select row_number() over(partition by C order by E DESC) no,a,b,c,d,e  

from t1

 

--将分组排序的查询当作一张表查询，需要按照上面排序，可以自己修改，这里处理为所描述的降序，根据no判断，小于等于5的就是需要的数据

 select *  

from (

select row_number() over(partition by C order by E DESC) no,a,b,c,d,e  

from t1

) a  

where a.no <= 5