CREATE TRIGGER myInsertTrigger

ON OrderItems

AFTER UPDATE

AS

DECLARE @Count INT;

SELECT @Count = (SELECT ItemCount from UPDATED)

BEGIN

IF(@Count>[OLD].ItemCount)

THEN

UPDATE Inventory

SET InventoryCount = InventoryCount - @Count

WHERE Inventory.ItemId IN(SELECT ItemId FROM UPDATED)

ELSEIF (@Count<[OLD].ItemCount)

THEN

UPDATE Inventory

SET InventoryCount = InventoryCount +...

what to do if more than one row is deleted ?

CREATE TRIGGER myTrigger

ON OrderItems

AFTER DELETE

AS

DECLARE @Count INT;

SELECT @Count = (SELECT ItemCount from Deleted)

BEGIN

UPDATE Inventory

SET InventoryCount = InventoryCount + @Count

WHERE Inventory.ItemId IN(SELECT ItemId FROM Deleted)

END

The correct one.

I my self found 😀