Complex query (Partision and Rank) to the rescue

Question

Hi all  
Given the table above:
I need to build a function, That when the TableID is passed to the function
It will sum the price of record with the same (ProductID, LocationID)
In this case it will sum the prices of TableID(1 and 2) The result will be 130
i.e the function will return 130. If it does not find a match. It will return null   
AKE

Answer 1

Will something like this be faster
WITH CTE (ProductID, LocationID, DuplicateCount)
 AS
   SELECT ProductID, LocationID,
   ROW_NUMBER() OVER(PARTITION BY ProductID, LocationID
    ORDER BY ProductID) AS DuplicateCount
    FROM MyTable
 SELECT *
 FROM CTE
 WHERE DuplicateCount > 1
 ORDER BY ProductID, LocationID, DuplicateCount
 GO
AKE