Defensive Database Programming - Red Gate Software

Chapter 6: Common Problems with Data Integrity@NewBarcode VARCHAR(20) ;-- retrieve the barcode before updateSELECT @ItemLabel = ItemLabel ,@OldBarcode = BarcodeFROM deleted ;-- retrieve the barcode after updateSELECT @NewBarcode = BarcodeFROM inserted ;PRINT 'old and new barcode as stored in variables' ;SELECT @OldBarcode AS OldBarcode ,@NewBarcode AS NewBarcode ;-- determine if the barcode changedIF ( ( @OldBarcode @NewBarcode )OR ( @OldBarcode IS NULLAND @NewBarcode IS NOT NULL)OR ( @OldBarcode IS NOT NULLAND @NewBarcode IS NULL))BEGIN ;INSERT INTO dbo.ItemBarcodeChangeLog( ItemLabel ,ModificationDateTime ,OldBarcode ,NewBarcode)VALUES ( @ItemLabel ,CURRENT_TIMESTAMP ,@OldBarcode ,@NewBarcode) ;END ;END ;Listing 6-46: The Items_LogBarcodeChange trigger logs changes made to theBarcode column of the Items table.194