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

FedIDNo,
DateInSystem)
VALUES
(‘MyCust’,
‘123 Anywhere’,
‘’,
‘Reno’,
‘NV’,
80808,
‘Joe Bob’,
‘555-1212’,
‘931234567’,
GETDATE());
Once again, we are able to INSERT non-conforming data to the table.
By now, you may be asking how you know whether you have the constraint turned on or not. It would
be pretty tedious if you had to create a bogus record to try to insert in order to test whether your constraint
is active or not. Like most (but not all) of these kinds of dilemmas, SQL Server provides a procedure
to indicate the status of a constraint, and it’s a procedure we’ve already seen,
sp_helpconstraint. To execute it against our Customers table is easy:
EXEC sp_helpconstraint Customers;
The results are a little too verbose to fit into the pages of this book, but the second result set this procedure
generates includes a column called status_enabled. Whatever this column says the status is can
be believed. In this case, it should currently be Disabled.
When we are ready for the constraint to be active again, we simply turn it back on by issuing the same
command with a CHECK in the place of the NOCHECK:
ALTER TABLE Customers
CHECK
CONSTRAINT CN_CustomerPhoneNo;
Chapter 6: Constraints
If you run the INSERT statement to verify that the constraint is again functional, you will see a familiar
error message:
Msg 547, Level 16, State 0, Line 1
The INSERT statement conflicted with the CHECK constraint
“CN_CustomerDateInSystem”. The conflict occurred in database “Accounting”, table
“dbo.Customers”, column ‘DateInSystem’.
The statement has been terminated.
Our other option, of course, is to run sp_helpconstraint again, and check out the status_enabled
column. If it shows as Enabled, then our constraint must be functional again.
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