Correlated join with outer fields as parameters - sql

Question

I need a way to join a table with a function's results. I'm not sure if it's possible and somehow I don't think it's a good idea. Let me try and explain the situation.
There is a table [Entities]:
[ID] [Description] [kWh] [kVArh] [kVAh] [OfferID] [CustomOfferID]
Another table [Data]:
[ID] [Timestamp] [Value]
And a function:
[Calc] (#offer, #customOffer, #kWh, #kVArh, #kVAh, #dtStart, #dtEnd)
So you can see there are entities, the entities' data (usage) and a function to calculate the cost.
I need to display the usage and cost of multiple entites:
[Description] [MWh] [MVA] [Cost]
[MWh] will be a SUM of all the entity's data over the period; [MVA] will be the MAX of all the data over the period; and [Cost] will SUM the [Cost] field from the sub query (function).
The query I figured would do the jobs looks like this:
SELECT [tc].[ID], [tc].[Desc]
, SUM([kWh].[Value]) / 1000 AS [MWh]
, MAX([kVAh].[Value]) / 1000 AS [MVA]
, SUM([cost].[Cost])
FROM [Tree_Cost] AS [tc]
INNER JOIN [Data] AS [kWh] ON [tc].[kWh] = [kWh].[ID]
INNER JOIN [Data] AS [kVAh] ON [tc].[kVAh] = [kVAh].[ID]
INNER JOIN
(
SELECT [tc].[ID], [Cost]
FROM [Calc] ([tc].[Offer_ID], [tc].[OfferCustom_ID], [tc].[kWh], [tc].[KVArh], [tc].[kVAh], #dtStart, #dtEnd)
) AS [cost] ON [tc].[ID] = [cost].[ID]
WHERE [tc].[Type] = 1 AND [tc].[TypeDesc] = 'GF_K_M'
AND [kWh].[Timestamp] BETWEEN #dtStart AND #dtEnd
AND [kVAh].[Timestamp] BETWEEN #dtStart AND #dtEnd
GROUP BY [tc].[ID], [tc].[Desc]
The real problem here is that I need to include the [ID] from the outer query in the result set of the inner query (function) in order to be able to join the two. Then I also need to be able to use the fields from the outer query as arguments for the inner query (function).
This is obviously not the way seeing as the [tc] identifier is not recognized in the inner query. So how am I supposed to accomplish something like this?
CREATE FUNCTION [dbo].[Calc]
( \#intOffer [int]
, \#intCustom [int]
, \#intP [int]
, \#intQ [int]
, \#intS [int]
, \#dtStart [datetime]
, \#dtEnd [datetime]
)
RETURNS TABLE
( [Entry] [nvarchar](200) NULL
, [Rate] [float] NULL
, [Unit] [nvarchar](50) NULL
, [Reading] [float] NULL
, [Cost] [float] NULL
, [DDate] [nvarchar](50) NULL
)
WITH EXECUTE AS CALLER
AS EXTERNAL NAME [OfferCalcLite].[UserDefinedFunctions].[SqlArray]

Answer 1

I'm not sure I understand correctly. Perhaps you can completely drop the JOIN:
INNER JOIN
(
SELECT [tc].[ID], [Cost]
FROM [Calc] ([tc].[Offer_ID], [tc].[OfferCustom_ID], [tc].[kWh], [tc].[KVArh], [tc].[kVAh], #dtStart, #dtEnd)
) AS [cost] ON [tc].[ID] = [cost].[ID]
and change:
, SUM([cost].[Cost])
into:
, SUM( [Calc] ( [tc].[Offer_ID]
, [tc].[OfferCustom_ID]
, [tc].[kWh]
, [tc].[KVArh]
, [tc].[kVAh]
, #dtStart, #dtEnd
)
) AS Cost