CREATE TRIGGER Items_PackagesChanges ON Items_Packages
FOR DELETE, INSERT, UPDATE
AS
BEGIN
 
UPDATE Packages
SET PackagePrice = TableOne.PackagePrice FROM
  (SELECT PackageId = Packages.PackageId,
  PackagePrice = SUM(((Products.ProductPrice * Products_Items.Quantity) * Items_Packages.Quantity) *.90)
  FROM Products
    INNER JOIN Products_Items ON Products.ProductId = Products_Items.ProductId
      INNER JOIN Items ON Products_Items.ItemID = Items.ItemID
      AND Items.ItemIsAvailable = 1
        INNER JOIN Items_Packages ON Items.ItemId = Items_Packages.ItemId
          INNER JOIN Packages ON Items_Packages.Packageid = Packages.PackageId
   GROUP BY Packages.PackageId)
AS TableOne 
  INNER JOIN Packages ON TableOne.PackageId = Packages.PackageId
  AND Packages.PackageId IN
/** next 3 lines are the new, correct subquery **/
 (SELECT DISTINCT PackageId FROM Items_Packages INNER JOIN
    (SELECT ItemId FROM Inserted UNION SELECT ItemId FROM Deleted) AS
TableTwo ON Items_Packages.ItemId = TableTwo.ItemID)
 
/** Next 3 lines are the old subquery 
 (SELECT DISTINCT Items_Packages.PackageId FROM Items_Packages
    LEFT OUTER JOIN Inserted ON Items_Packages.ItemID = Inserted.ItemId
      LEFT OUTER JOIN Deleted ON Items_Packages.ItemId = Deleted.ItemId)
**/
 
END