Re: Populate unique column with default value

I guess what i'm looking for is something like the following, but i
don't know how i'd do it.

"UPDATE usertable SET username='SELECT extension FROM usertable WHERE
id=<current row>' WHERE username ISNULL",

Is this possible?

Thanks,

Jon.

On 10/1/07, Jon Horsman <horshaq(at)gmail(dot)com> wrote:
> Hey,
>
> I'm updating the user table in our db to have a new column "username"
> as follows.
> ALTER TABLE usertable ADD COLUMN username varchar(64)
> UPDATE usertable SET username='<extension of current row>' WHERE username ISNULL
> ALTER TABLE usertable ALTER COLUMN username SET NOT NULL
> ALTER TABLE usertable ADD CONSTRAINT usertable_username_key UNIQUE(username)
>
> I want to essentially do what i have above but need to populate the
> username field with some unique value so that the last ALTER will run.
> I have another column in this table that is unique, an phone
> extension, and am hoping to use this as a default username. Is there
> an elegant way i can set the username to be the extension of the
> current row or should i just write a little loop that goes threw and
> populates my username with the users extension manually for each user
> in my db and then run the last ALTER.
>
> Thanks,
>
> Jon.
>