Question

I am trying to add a column (MSSQL 2005) to a table (Employee) with a default constraint of a primary key of another table (Department). Then I am going to make this column a FK to that table. Essentially this will assign new employees to a base department based off the department name if no DepartmentID is provided.
This does not work:

DECLARE     @ErrorVar       INT DECLARE     @DepartmentID       INT  SELECT      @DepartmentID = DepartmentID FROM        Department WHERE       RealName = 'RocketScience'  ALTER TABLE     [Employee] ADD             [DepartmentID] INT NULL CONSTRAINT      [DepartmentIDOfAssociate] DEFAULT (@DepartmentIDAssociate) SELECT @ErrorVar = @@Error IF (@ErrorVar <> 0) BEGIN     GOTO FATAL_EXIT END 

The Production, Test, and Development databases have grown out of synch and the DepartmentID for the DepartmentName = ‘RocketScience’ may or may not be the same so I don’t want to just say DEFAULT (somenumber). I keep getting “Variables are not allowed in the ALTER TABLE statement” no matter which way I attack the problem.
What is the correct way to do this? I have tried nesting the select statement as well which gets “Subqueries are not allowed in this context. Only scalar expressions are allowed.”

In Addition, what would be really great I could populate the column values in one statement instead of doing the

{ALTER null}
{Update values}
{ALTER not null}

steps. I read something about the WITH VALUES command but could not get it to work. Thanks!!!

Answer 1

You could wrap the code to find your department ID into a stored function and use that in your DEFAULT constraint statement:

CREATE FUNCTION dbo.GetDepartment() RETURNS INT AS BEGIN   DECLARE         @DepartmentID           INT    SELECT          @DepartmentID = DepartmentID   FROM            Department   WHERE           RealName = 'RocketScience'    RETURN @DepartmentID END 

And then:

ALTER TABLE     [Employee] ADD                     [DepartmentID] INT NULL CONSTRAINT      [DepartmentIDOfAssociate] DEFAULT (dbo.GetDepartment()) 

Does that help?

Marc