>>>>>>>>>>>> adedayo damilola wrote (2007-08-16 14:05:27): > After reading the Derby document(s) I discovered that the UNIQUE > constraint in Derby does not allow NULL values to be inserted into a > cloumn with the constraint applied. So I was wondering if there was > another way to achieve since the UNIQUE constraint was designed to > do this
UNIQUE on nullable columns is optional feature T591 in the SQL standard and is not implemented in Derby. There is some work going on and there is a fair chance that this will be implemented for the next release. If you want to achieve an enforcement of an unique constraint by other means, I think it is possible to do it with a trigger, but it will not be very performant. -- Bernt Marius Johnsen, Database Technology Group, Staff Engineer, Technical Lead Derby/Java DB Sun Microsystems, Trondheim, Norway
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