if OBJECT_ID('tb') is not null Drop table tb;
go

create table tb(A int, B varchar(14), C int);
go
insert into tb(A, B, C)
select 1, 'A', 5 union all 
select 1, 'D', 1 union all 
select 1, 'C', 2 union all 
select 3, 'XL', 4 union all 
select 3, 'RL', 6 union all 
select 3, 'JK', 2 union all 
select 7, 'U', 4;

select t.A,t.B,t.C
from (
        select rn=ROW_NUMBER() over(partition by A order by A,C)
            , *
        from tb
    ) t
order by t.rn, t.A

/*
A           B              C
----------- -------------- -----------
1           D              1
3           JK             2
7           U              4
1           C              2
3           XL             4
1           A              5
3           RL             6
*/

------解决方案--------------------
SQL code
if OBJECT_ID('tb') is not null Drop table tb;
go

create table tb(A int, B varchar(14), C int);
go
insert into tb(A, B, C)
select 1, 'A', 5 union all 
select 1, 'D', 1 union all 
select 1, 'C', 2 union all 
select 3, 'XL', 4 union all 
select 3, 'RL', 6 union all 
select 3, 'JK', 2 union all 
select 7, 'U', 4;
select A, B, C
from (
        select rn = (    select count(1) 
                        from tb b 
                        where b.A = a.A and b.C < = a.C )
              , a.*
        from tb a 
      )t
order by rn, A