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From Dan Meany <dan_me...@yahoo.com>
Subject Unique constraints on multiple fields with one nullable
Date Wed, 26 Oct 2005 22:36:34 GMT
I noticed that in Derby a unique constraint on two
columns A and B, with B nullable, will prevent
inserting two identical records that contain NULL in

This is different from some other databases such as
Sybase that do allow it (I assume where the null
records are not in stored as part of the unique

I noticed this while transfering data from Sybase to
Derby using Apache dbutils and getting rejected
duplicate records.

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