vanderghast replied to Nick X
18-Mar-10 02:47 PM
Jet consider that two null are not duplicated, but MS SQL Server consider
that they are, as far as indexes are concerned. In other words, Jet will
accept two null under a field with a UNIQUE constraint on it, but MS SQL
Server will not (because it considers that a null duplicates another null).
For info, that is one of the point where Jet is accordingly to the standard
while MS SQL Server is not (and unlikely to ever be, due to historical
behavior).
Vanderghast, Access MVP