Den 2012-04-24 10:18 skrev Thomas Steinmaurer såhär: > > > 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. It didn't cross my mind that it could be different... SQL Server UNIQUE allows only a single null. I really think this should be optional, e.g. like this: 1. constraint X unique (Y) ignore null 2. constraint X unique (Y) restrict null 1 would be like FB, 2 like SQL Server. Kjell -- -------------------------------------- Kjell Rilbe DataDIA AB E-post: [email protected] Telefon: 08-761 06 55 Mobil: 0733-44 24 64 [Non-text portions of this message have been removed] ------------------------------------ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Visit http://www.firebirdsql.org and click the Resources item on the main (top) menu. Try Knowledgebase and FAQ links ! Also search the knowledgebases at http://www.ibphoenix.com ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/firebird-support/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/firebird-support/join (Yahoo! ID required) <*> To change settings via email: [email protected] [email protected] <*> To unsubscribe from this group, send an email to: [email protected] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
