Question

I currently have a table like this:

    Stuff
    ----------
    StuffId identity int not null
    Description nvarchar(4000) null
    ...

I want to store the Description in a separate table that I have set aside specifically for user-generated content:

    Content
    ----------
    ContentId identity int not null
    Content nvarchar(max) not null
    ...

(this table already exists, and other tables already reference entries in it.)

So I need to:

1. Create a DescriptionContentId field on the Stuff table with a foreign key constraint.
2. Copy the current Description content into the Content table.
3. Set each DescriptionContentId to have the ContentId value that was automatically generated when inserting values in step 2.
4. Drop the Description column.

I know how to do steps 1 and 4, but steps 2 and 3 are eluding me, because they need to be done pretty much simultaneously. This seems like it would be a fairly common schema change. What’s the best way to do it?

Update

I’m a step closer thanks to the Output keyword, but I’m still missing something. Here’s what I’d like to do:

create table #tmp (StuffId int, ContentId int)

insert into Content(Content)
output s.StuffId, inserted.ContentId
into #tmp(StuffId, ContentId)
    select Description
    from Stuff s
    where Description IS NOT NULL

But I can’t reference s.StuffId because it isn’t one of the fields inserted into the Content table. How can I correlate the ID of the Stuff with the ID of the Content as I’m inserting a new Content item for each Stuff entry?

Answer 1

The output clause will come to your rescue.

It will output the description and the identity column from the insert into a table varaible and then you can use that data to update the other table.

If description is not unique, you may have to do the following:
add a column for the stuffID column to the content table. Then output the stuffid and content id from the insert, update the table using the stuffid to ensure uniqueness, Drop the stuffid column from the content table.

an example from Books Online as to how to use the OUTPUT

DECLARE @MyTableVar table(
  LastName     nvarchar(20) NOT NULL,
  FirstName    nvarchar(20) NOT NULL,
  CurrentSales money NOT NULL
  );

INSERT INTO dbo.EmployeeSales (LastName, FirstName, CurrentSales)
  OUTPUT INSERTED.LastName, 
         INSERTED.FirstName, 
         INSERTED.CurrentSales
  INTO @MyTableVar
    SELECT c.LastName, c.FirstName, sp.SalesYTD
    FROM HumanResources.Employee AS e
        INNER JOIN Sales.SalesPerson AS sp
        ON e.EmployeeID = sp.SalesPersonID 
        INNER JOIN Person.Contact AS c
        ON e.ContactID = c.ContactID
    WHERE e.EmployeeID LIKE '2%'
    ORDER BY c.LastName, c.FirstName;