Well, the Date argument against NULLs (and he never endorsed them, or
so he claims) is that they are not data- they represent the absence of
data- so why put non-data in a _data_base.
If you are asking yourself the question how you can have support
multiple meanings in a column, normalize. Then, baldness is just
another value and you don't have to guess if the hair color is unknown,
undefined, or missing.
On Jun 8, 2006, at 10:10 PM, Christopher Browne wrote:
> 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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> [name;tld];;
> http://linuxdatabases.info/info/lisp.html
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AgentM
agentm@themactionfaction.com
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