Create Trigger trgTest ON TableName
FOR INSERT,UPDATE,DELETE
AS
IF NOT EXISTS(SELECT * From StockTable,inserted WHERE StockTable.ID=inserted.ID)
INSERT INTO StockTable SELECT ID,0 from inserted
UPDATE StockTable
SET OrderAmt=OrderAmt+(ISNULL(inserted.OAmt,0)-ISNULL(deleted.OAmt,0))
From StockTable INNER JOIN ( inserted FULL OUTER JOIN deleted ON inserted.ID=deleted.ID)
ON StockTable.ID=ISNULL(inserted.ID,deleted.ID)