聯合選擇只有一行

Question

我有一個查詢與兩個選擇條款聯合使用UNION.I只想選擇第一行。我如何使用聯盟？

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

這將返回2行：

select 1 as id 
union 
select 2 as id 

這將返回1行：

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