UNIQUE constraint on posisble null columns (Was: DB2 mode vs. Cloudscape mode)

["Bernt M. Johnsen" <be...@sun.com>]

>>>>>>>>>>>> Satheesh Bandaram wrote (2005-03-03 16:39:11):
> Yes, Cloudscape used to allow creating UNIQUE indexes on null columns,
> but in a non-standard way. Old cloudscape used to allow only one NULL
> value in the UNIQUE index, where as, I think the standard required
> multiple NULL values.

I think that behaviour was Oracle compliant.

> I think making Derby handle multiple NULLs in UNIQUE index needs changes
> to store/indexing.

Anyway, UNIQUE constraint on possible null columns (SQl-99 Feature
T591) is a non-Core SQL-99 feature.

-- 
Bernt Marius Johnsen, HA Data Management, Sun Microsystems, Norway
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