TSQL：如何输出记录，即使条件不匹配

Question

我有一个临时表，包含3列“ID”，“成本”，“MaxCost”..下面是我的选择语句，它选择给定特定ID的行。

 SELECT 
      t.Cost 
      t.MaxCost 
     FROM @temp t 
     WHERE t.ID = @ID   

如何修改上面的查询，这样即使给定的ID不符合成本= 0 & MaxCost = 0

Answer 1

选择这两个实际和默认的记录存在它仍然输出行，并选择第一个按重量排序。

select top (1) 
    Cost, 
    MaxCost 
from (
    SELECT 
    t.Cost 
    t.MaxCost, 
    1 as takeme 
    FROM @temp t 
    WHERE t.ID = @ID 

    union all 

    select 0, 0, 0 
) foo 
order by 
    foo.takeme desc 

Answer 2

declare @table table (cost int); 
insert into @table values (2), (2), (3); 

declare @findCost int = 1; 

select * from @table where cost = @findCost 
union all 
select 0 as cost from @table where cost = @findCost having count(*) = 0; 

set @findCost = 2; 

select * from @table where cost = @findCost 
union all 
select 0 as cost from @table where cost = @findCost having count(*) = 0;