CREATE FUNCTION [dbo].[ufnGetProductDealerPrice](@ProductID [int], @OrderDate [datetime])
RETURNS [money]
AS
-- Returns the dealer price for the product on a specific date.
BEGIN
   DECLARE @DealerPrice money;
   DECLARE @DealerDiscount money;

   SET @DealerDiscount = 0.60  -- 60% of list price

   SELECT @DealerPrice = plph.[ListPrice] * @DealerDiscount
   FROM [Production].[Product] p
       INNER JOIN [Production].[ProductListPriceHistory] plph
       ON p.[ProductID] = plph.[ProductID]
           AND p.[ProductID] = @ProductID
           AND @OrderDate BETWEEN plph.[StartDate] AND COALESCE(plph.[EndDate], CONVERT(datetime, '99991231', 112)); -- Make sure we get all the prices!

   RETURN @DealerPrice;
END;
GO
EXEC sp_addextendedproperty N'MS_Description', N'Scalar function returning the dealer price for a given product on a particular order date.', 'SCHEMA', N'dbo', 'FUNCTION', N'ufnGetProductDealerPrice', NULL, NULL
GO
EXEC sp_addextendedproperty N'MS_Description', N'Input parameter for the scalar function ufnGetProductDealerPrice. Enter a valid order date.', 'SCHEMA', N'dbo', 'FUNCTION', N'ufnGetProductDealerPrice', 'PARAMETER', N'@OrderDate'
GO
EXEC sp_addextendedproperty N'MS_Description', N'Input parameter for the scalar function ufnGetProductDealerPrice. Enter a valid ProductID from the Production.Product table.', 'SCHEMA', N'dbo', 'FUNCTION', N'ufnGetProductDealerPrice', 'PARAMETER', N'@ProductID'
GO