I have a query that takes too long to execute.
I need to know if there is any optimum way of executing that to reduce execution time.

my query is 

```
SELECT     TOP (2) ID,
                   (
                    SELECT     SUM(CurrentStock) AS SimilarItemQuantity
                    FROM          Inventory AS T1
                    WHERE      (Inventory.ProductName = ProductName)
                   ) 
                   AS Expr1
FROM         Inventory

```

Consider that for 20 records and it takes 15 seconds.
Is there a more faster way of doing it.