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From "Bernt M. Johnsen" <Bernt.John...@Sun.COM>
Subject Re: unique columns must be nullable ?
Date Tue, 12 Dec 2006 10:28:09 GMT
>>>>>>>>>>>> Xanana Gusmao wrote (2006-12-12 04:08:39):
> On this page http://wiki.apache.org/db-derby/HibernateHelp
> it says:
> "Hibernate Annotations do not work because Derby does not allow a unique column
> to be nullable"
> Is this (that Derby's unique column must be non-nullable) still true
> ?

That's still true. UNIQUE constraint on nullable columns is optional
feature T591 in the SQL standard and not implemented in Derby. See

For a longer discussion of the topic, see

Bernt Marius Johnsen, Database Technology Group, 
Staff Engineer, Technical Lead Derby/Java DB
Sun Microsystems, Trondheim, Norway

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