create table tb
(type char(1), val int)

insert into tb
select 'A', 3 union all
select 'A', 7 union all
select 'B', 2 union all
select 'C', 12 union all
select 'A', 23 union all
select 'A', 33 union all
select 'C', 29 union all
select 'C', 10 union all
select 'B', 13 union all
select 'B', 56 union all
select 'C', 21


with t as
(select row_number() over(partition by [type] order by val desc) rn,
 [type],[val] from tb
)
select [type],[val]
from t
where rn<=3

/*
type  val
---- -----------
A     33
A     23
A     7
B     56
B     13
B     2
C     29
C     21
C     12

(9 row(s) affected)
*/

------解决方案--------------------

SQL code

select type ,val
from 
(
select  type ,val,row_number() over(partition by type order by val desc) as rn
from TB) a
where a.rn<=3