-- A function to add two ints and return an int
create function AddNumbers_Scalar(@a int, @b int) 
  returns int 
as begin
	return (@a + @b)
end
go
-- A function to add two integers and return the 
-- result in a table variable
create function AddNumbers_Table(@a int, @b int) 
   returns @fnord table(foo int) 
as begin 
	insert into @fnord(foo) values(@a + @b)
	return
end
go
declare @w int
declare @x int
declare @y int
declare @z int

set @w = 1
set @x = 1
set @y = 1
set @z = 1

declare @m int
declare @n int

set @m = @w + @x
set @n = @y + @z

-- These both return 4 - so far, so good!
select dbo.AddNumbers_Scalar(@m, @n)
select * from dbo.AddNumbers_Table(@m, @n)

-- This returns 4...
select dbo.AddNumbers_Scalar(@w + @y, @y + @z)
-- ...but this says "Incorrect syntax near '+'."
select * from dbo.AddNumbers_Table(@w + @x, @y + @z)