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

Chapter 6: Constraints
Defining a DEFAULT Constraint in Your
CREATE TABLE Statement
174
Under the heading of “One more thing,” it’s worth noting that there is an exception
to the rule about an UPDATE command not using a default. The exception happens if
you explicitly say that you want a default to be used. You do this by using the keyword
DEFAULT as the value you want the column updated to.
At the risk of sounding repetitious, this works pretty much like all the other column constraints we’ve
dealt with thus far. You just add it to the end of the column definition.
To work an example, start by dropping the existing Shippers table that we created earlier in the chapter.
This time, we’ll create a simpler version of that table, including a default:
CREATE TABLE Shippers
(
ShipperID int IDENTITY NOT NULL
PRIMARY KEY,
ShipperName varchar(30) NOT NULL,
DateInSystem smalldatetime NOT NULL
DEFAULT GETDATE ()
);
After you run your CREATE script, you can again make use of sp_helpconstraint to show you what
you have done. You can then test how your default works by inserting a new record:
INSERT INTO Shippers
(ShipperName)
VALUES
(‘United Parcel Service’);
Then run a SELECT statement on your Shippers table:
SELECT * FROM Shippers;
The default value has been generated for the DateInSystem column since we didn’t supply a value
ourselves:
ShipperID ShipperName DateInSystem
-------------------------------------- ---------------------------
1 United Parcel Service 2008-07-31 23:26:00
(1 row(s) affected)