--数据建表
drop table if exists db.tb_name;
create table if not exists db.tb_name
( `name` string
	,`class` string
	,score string
)
;
insert overwrite table db.tb_name
values
("a","1","100")
,("b","1","99")
,("c ","1","99")
,("d","2","100")
,("e ","2","100")
,("f ","3","86")
,("g","3","99")
,("h","3","99")
;

1.row_number()

select a.*
	,row_number() over (partition by `class` order by cast(score as bigint) desc) as rn
from 
db.tb_name a
;

查询到的排序结果如下：

2.rank()

select a.*
	,rank() over (partition by `class` order by cast(score as bigint) desc) as rn
from 
db.tb_name a
;

查询到的排序结果如下：

3.dense_rank()

select a.*
	,dense_rank() over (partition by `class` order by cast(score as bigint) desc) as rn
from 
db.tb_name a
;

查询到的排序结果如下：

通过以上三种实例演示，发现row_number（）不存在相同位次的情况，即使值大小一致，但在排序的时候，也会顺延往下一位。rank()若存在相同位次，下一个位次的计算会跳过之后的位次，即排名相等会在名次中留下空位。dense_rank()若存在相同位次，下一个位次的计算不会跳过之后的位次，即虽然存在相同位次的情况，但是位次是连续不间断的，即排名相等不会在名次中留下空位。