A long time ago, in a galaxy far, far away, tshipley@deru.com (Trent Shipley) wrote:
> On Thursday 2006-06-08 15:14, David Fetter wrote:
>> On Thu, Jun 08, 2006 at 05:21:07AM -0700, dananrg@yahoo.com wrote:
>
>> on bag theory[1] and 3-value logic[2]. Until they come up with a
>> testable system, or Hell freezes over, whichever comes first,
>> Pascal's book will make a good companion on your shelf to books on
>> Phlogiston[3] theory, or a decent doorstop, whichever you prefer.
>
> I have encountered at least two commercial database products that
> declared every column "NOT NULL". I have always assumed that this
> was defensive, preventing stupid programmer mistakes.
>
> I recall reading somewhere that Codd proposed multiple flavors of
> nullity. Are there theoretical proposals for databases with logical
> systems having more than three values?
Darwen did a paper where he described how you'd cope with not having
any nulls. It amounted to having a whole bunch of views that would
have a whole host of special indicator values to replace the multiple
meanings of NULL...
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