sql - 1行だけユニオン選択

Question

2 つの Select 句と UNION を組み合わせたクエリがあります。先頭の最初の行のみを選択したいです。Union を使用してそれを行うにはどうすればよいですか?

Select Fault,OccurredOn From ATMStatus Where Ticket=189703 // This Will retrieve single record as the primary key is applied
Union 
Select Fault,OccurredOn From ATMStatusHistory Where Resolved=0 AND Ticket=189703 Order By OccurredOn Desc

Answer 1

select top 1 * from 
(
                 Select Fault,OccurredOn 
                 From ATMStatus
                 Where Ticket=189703
                 Union 
                 Select Fault,OccurredOn
                 From ATMStatusHistory
                 Where Resolved=0 AND Ticket=189703
) x
Order By OccurredOn Desc

Answer 2

これは 2 行を返します。

select 1 as id
union
select 2 as id

これは 1 行を返します。

select top 1 * from (
  select 1 as id
  union
  select 2 as id
) as x
order by id