Den 2012-04-24 10:39 skrev Thomas Steinmaurer s�h�r:

>
> > Den 2012-04-24 10:18 skrev Thomas Steinmaurer s�h�r:
> >>
> >>> Is there any way to enforce uniqueness of all non-nulls in a nullable
> >>> column?
> >>
> >>> The "business requirement" would be "this kind of thing has an
> optional
> >>> attribute, that, if it exists, is unique". For example, a company
> may or
> >>> may not exist in the Byro van Dijk company database, but if it does
> >>> exist it will have a unique BvD id. I'd like to enforce this
> uniqueness.
> >>
> >> I'm sure I don't understand the question properly, because a Firebid
> >> UNIQUE constraint on a null-able column doesn't take NULLs into
> account,
> >> as long as it isn't a compound UNIQUE constraint made up from> 1
> >> columns..
> >>
> >>
> >>
> >
> > Oh!? I didn't know. RTFM then... :-) I was working in SQL Server and
> > then this cropped up.
>
> Yeah, welcome in the world writing applications supporting multiple
> backends. Little, neat differences along different products. ;-)
>
> Regards,
> Thomas
>
>

Been doing that since about 1997 actually. Don't know why it didn't
occur to me this time. But it wasn't an app - just some ad hoc data work
- import data from external source.

Kjell

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Kjell Rilbe
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