select @@VERSION
create table #t1 (col int not null)
create table #t2 (col int not null)
create table #t3 (col int not null)

insert #t1 values (1), (1)
insert #t2 values (2)
insert #t3 values (3)

select COL from #t1
UNION
select COL from #t2
union all
select COL from #t3

select COL from #t1
UNION ALL
select COL from #t2
union all
select COL from #t3