Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Let’s go ahead and test out our handiwork. First, we need a record or two that will fail when it hits our
trigger. Unfortunately, AdventureWorks2008 has apparently never discontinued a product before — we’ll
just have to change that…
UPDATE Production.Product
SET DiscontinuedDate = ‘01-01-2008’
WHERE ProductID = 680
Now, knowing that we have a discontinued product, let’s go ahead and add an order detail item that
violates the constraint. Note that I’ve chosen an existing order (43659) to tack this item onto:
INSERT INTO Sales.SalesOrderDetail
VALUES
(43659, ‘4911-403C-98’, 1, 680, 1, 1431.50,0.00, NEWID(), GETDATE())
This gets the rejection that we expect:
Msg 50000, Level 16, State 1, Procedure SalesOrderDetailNotDiscontinued, Line 14
Order Item is discontinued. Transaction Failed.
Msg 3609, Level 16, State 1, Line 1
The transaction ended in the trigger. The batch has been aborted.
Remember that we could, if desired, also create a custom error message to raise, instead of the ad hoc
message that we used with the RAISERROR command.
If you’re working along with these, but trying to keep your AdventureWorks2008 database close to its
original state, don’t forget to return ProductID 680 back to its null discontinued date.
Using Triggers to Check the Delta of an Update
Sometimes, you’re not interested as much in what the value was or is, as you are in how much it changed.
While there isn’t any one column or table that gives you that information, you can calculate it by making
use of the Inserted and Deleted tables in your trigger.
To check this out, let’s take a look at the Production.ProductInventory table. ProductInventory
has a column called Quantity. Recently, there has been a rush on several products, and Adventure-
Works2008 has been selling out of several things. Since AdventureWorks2008 needs more than just a few
customers to stay in business in the long run, it has decided to institute a rationing system on their products.
The Inventory department has requested that we prevent orders from being placed that try to sell
more than half of the units in stock for any particular product.
To implement this, we make use of both the Inserted and Deleted tables:
CREATE TRIGGER Production.ProductIsRationed
ON Production.ProductInventory
FOR UPDATE
AS
Chapter 15: Triggers
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