TSQL: How to ouput records even when where condition doesnt match

Question

I have a temp table with 3 columns "ID","Cost", "MaxCost"..below is my select statement which selects rows given particular ID..

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

How do i modify the above query so that even if given ID doesn't exists it still output rows with Cost = 0 & MaxCost = 0

Answer 1

Select both the actual and the default record, and select the first one ordering by their weight.

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