create table tbl_order
(
id_order int
,type nvarchar(40)
)

insert into tbl_order (id_order, type) values (1234, 'A' )
insert into tbl_order (id_order, type) values (1235, 'A' )
insert into tbl_order (id_order, type) values (1235, 'B' )
insert into tbl_order (id_order, type) values (1236, 'B' )
insert into tbl_order (id_order, type) values (1237, 'C' )
insert into tbl_order (id_order, type) values (1237, 'D' )
insert into tbl_order (id_order, type) values (1238, 'A' )
insert into tbl_order (id_order, type) values (1239, 'D' )
insert into tbl_order (id_order, type) values (1239, 'B' )
insert into tbl_order (id_order, type) values (1239, 'A' )


select 
	id_order
	,type
	--,isnull(orderX,'') as number
	,case when orderX > 1 then 1 else 0 end as number2
 from tbl_order
	left join (select t2.id_order as orderX
				from tbl_order as t2
				where	
					(select count(t1.id_order) 
						from tbl_order as t1 
						where 
							t1.id_order = t2.id_order) = 1
			)as  x
	on tbl_order.id_order = x.orderX