Re: c.d.theory glossary 0.0.4 [NULL]

From: Dawn M. Wolthuis <dwolt_at_tincat-group.comREMOVE>
Date: Thu, 30 Sep 2004 17:21:39 -0500
Message-ID: <cji0u6$u54$1_at_news.netins.net>


"mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message news:415c6c73$0$10528$e4fe514c_at_news.xs4all.nl...
> [NULL]
> The insanity bit. No! The humility marker.
> mu: The absence of an answer to a question which requires an answer.
>
> /adj./
> Attributes to something the absence of values.
> Ex: "The *null* set is the empty set, often represented by {}."

The null set is an example of "null" HAVING a value -- the value of an empty set. Some database theories have null as a "no value" or "absense of value" while others attribute a value to NULL, as in "null set".

> /n. colloq./
> A noted appearance of the absence of values.
> Ex: "This table contains *nulls*."
>
> Confusion arises when people use terms like "null value",
> a paradox to some, a contradictio in terminis to others.

[Quoted] [Quoted] And to others a perfectly useful concept. This depends more on your [Quoted] database implementation than on the theory. There could be relational databases as well as non-relational databases that hold to null as a value. [Quoted] SQL, on the other hand, has null as a non-value.

> 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.)

[Quoted] The confusion arises more because some products interpret null as a value (especially those that employ a two-valued logic) while others, SQL in particular, interpret null as a non-value although SQL is said to have a three-valued logic.

> In some contexts, 'null' and 'nil' mean the same thing;
> in others, they do not.
>
> In databases traditionally NULL is used and opposed.

[Quoted] In relational databases, ...

> Here is some opposition:
> How to distinguish between "missing" and "empty"?
>
> Lestrade: "Is there anything to which you wish
> to draw my attention?"
> Holmes: "To the curious incident of the dog in the night."
> Lestrade: "The dog did nothing in the night."
> Holmes: "That was the curious incident."
>
> 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

The quotations are great. --dawn Received on Fri Oct 01 2004 - 00:21:39 CEST

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