declare @A table (dm varchar(3),jc varchar(2))
insert into @A
select '001','上' union all
select '002','下' union all
select '003','上' union all
select '004','下'

declare @B table (dm varchar(3),km int)
insert into @B
select '001',1 union all
select '001',2 union all
select '002',1 union all
select '002',2 union all
select '002',3 union all
select '003',3

select d.dm,d.col from (select * from @A a 
cross join (select 1 as col union select 2 union select 3)c
where a.dm in (select dm from @B))d
full join  @B b on d.col=b.km and d.dm=b.dm where b.km is null order by 1
/*
dm   col
---- -----------
001  3
003  1
003  2
*/