> >> Second, it seems logical that if I have UNIQUE then I don't have to > >> declare NOT NULL. For example, > > > > Not redundant. UNIQUE does not imply NOT NULL. > > thanks for all the valuable clarification. However, the above seems > contradictory. After all, if more than one row can be NULL, then they > won't be UNIQUE! what gives?
If only one value in the table is null, and the rest have non-null unique values, that satisfies the UNIQUE requirement.
