Recursive Stored Procedure

Create PROCEDURE Factorial
@Number as int,
@Factorial as int OUTPUT

AS
Begin

DECLARE @Input int
DECLARE @Output int
IF @Number != 1

BEGIN
set @Input = @Number - 1
EXEC Factorial @Input, @Output OUTPUT
SELECT @Factorial = @Number * @Output
END

ELSE
BEGIN
SELECT @Factorial = 1
END

RETURN
End