ALTER FUNCTION [dbo].[fn_BugunYasHesapla](@DogumTarihi datetime,@Bugun datetime)
RETURNS INT
AS
BEGIN 
Declare @Yas int
set @Yas=(SELECT 
	DATEDIFF(YEAR,@DogumTarihi,@Bugun) 
	-CASE 
	WHEN DATEADD(YY,DATEDIFF(YEAR,@DogumTarihi,@Bugun),@DogumTarihi)>@Bugun
	THEN 1 
	ELSE 0 
END AS DogumTarihi)
RETURN @Yas
END
SELECT dbo.fn_BugunYasHesapla('27.01.1979',getdate()) as Yas
 