SQL - Crear una función escalar que regrese el empleado que vendió mayor cantidad de productos

SELECT Employees.EmployeeID, SUM([Order Details].Quantity) FROM  [Order Details] INNER JOIN Orders ON [Order Details].OrderID=Orders.OrderID INNER JOIN Employees ON Employees.EmployeeID=Orders.EmployeeID GROUP BY Employees.EmployeeID

CREATE FUNCTION EmpleadoQueVendioMas () RETURNS int

  AS

  BEGIN

    DECLARE @Empleado int

    SELECT TOP 1 @Empleado=Employees.EmployeeID  FROM  [Order Details] INNER JOIN Orders ON [Order Details].OrderID=Orders.OrderID INNER JOIN Employees ON Employees.EmployeeID=Orders.EmployeeID GROUP BY Employees.EmployeeID ORDER BY SUM([Order Details].Quantity) DESC

    RETURN @Empleado

  END