NULL (was: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens])

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Tue, 07 Jun 2005 23:14:43 +0200
Message-ID: <42a60e41$0$45447$e4fe514c_at_news.xs4all.nl>


Jan Hidders wrote:
> Marshall Spight wrote:
>

>>> Most of the time, in database context NULL denotes, as you point out,
>>> the _absence_ of a value where you would expect one - still you are
>>> freely using "NULL value" as a special kind of value.
>>
>> In fact, I don't think this is true. The SQL standard mostly takes
>> the stand that NULL means "there is a value, but we don't know
>> what it is."

>
> As a small side note: the reason that the "mostly" above is not
> "completely" is because that would make the result of an SQL query
> uncomputable.

Earlier I wrote (in fact _we_ wrote, I summarized):

> [NULL]
> The insanity bit. No! The humility marker.
> mu: The absence of an answer to a question which requires an answer.
>
> /adj./
> 1. Attributes to something the absence of values.
> Ex: "The *null* set is the empty set, often represented by {}."
>
> /n. colloq./
> 1. A noted appearance of the absence of values.
> Ex: "This table contains *nulls*."
>
> Common usage:
>
> - Confusion arises when people use terms like "null value",
> a paradox to some, a contradictio in terminis to others.
>
> - Confusion arises due to the fact that nullness (the absence of value)
> is often represented on computers by the number 0.
> (Obviously, 0 is not null.)
>
> - In some contexts, 'null' and 'nil' mean the same thing; in others,
> they do not.
>
> In databases traditionally NULL is used and and opposed.
> If you want to go into this, please first search for
> mu NIL void NULL undef, 2VL 3VL.
>
> "It isn't the things we don't know that give us trouble.
> It's the things we know that ain't so." - Will Rogers

I now think this is to much from the "NULL is the absence of value" point of view. Any suggestions for improvement? Received on Tue Jun 07 2005 - 23:14:43 CEST

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