Question

我有一个包含3列“ID”，“Cost”，“MaxCost”的临时表。下面是我的select语句，它选择给定特定ID的行..

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

如何修改上述查询，以便即使给定ID不存在，它仍然会输出Cost = 0＆amp; MaxCost = 0

Answer 1

选择实际和默认记录，然后按权重选择第一个排序。

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;

TSQL：即使条件不匹配，如何输出记录

2 个答案: