Subject Re: [firebird-support] Uniqueness among non-null values in nullable column?
Author Thomas Steinmaurer
> 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.

With regards,
Thomas Steinmaurer (^TS^)
Firebird Technology Evangelist

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