create table #t1(k int, v varchar( 50 ))
create table #t2(k int, v varchar( 50 ))

insert #t1 values( 1 , 'one') 
insert #t1 values( 2 , 'two' )
insert #t1 values( 3 , 'thre' )
insert #t1 values( 4 , 'fore' )
insert #t1 values( 5 , 'five')


insert #t2 values( 1 , 'one1') 
insert #t2 values( 1 , 'one2' )
insert #t2 values( 2 , 'two1' )
insert #t2 values( 2 , 'two2' )
insert #t2 values( 5 , 'five1' )

select a.k, a.v, (select top  1  b.v from #t2 b where b.k=a.k) as t2_v
from #t1 a

drop table #t1
drop table #t2