NULL

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Fri, 01 Oct 2004 01:52:54 +0200
Message-ID: <415c9c59$0$78738$e4fe514c_at_news.xs4all.nl>


Sorry for changing the subject line.
This is not glossary stuff, I think
it's worth discussing in its own right.

Dawn M. Wolthuis wrote:

> mAsterdam quoted:

>>Confusion arises when people use terms like "null value",
>>a paradox to some, a contradictio in terminis to others.

>
> And to others a perfectly useful concept.

Very useful, definitely. It's use would not have become so widely spread otherwise.
"perfectly" - I don't think so.
"concept" - or filler for the lack of one.

> This depends more on your
> database implementation than on the theory.

Implementors have to deliver.
If somebody could shed some light
on the early history of NULL in databases, I would be grateful. Pure curiosity.

> There could be relational
> databases as well as non-relational databases that hold to null as a value.

Agreed. Nuance:
Whenever somebody (forced or not) decides to represent the absence of a value (s)he has to decide *how* (with which sign) to
represent this absence. So there will be a sign, a value of some kind, to represent the absence of a value on another level. It has to be on another level, because on this one the dice are thrown: there *is* a value. Next problem: what are these levels.

> SQL, on the other hand, has null as a non-value.

Dunno. Don't care.

>>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.)

>
> 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.

I said I don't care! (Oh well, you didn't read that yet when you wrote this :^)
My daughter (13), yesterday in a conversation: "Don't laugh unless you think otherwise".

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

>
> In relational databases, ...
Ok.

> The quotations are great. --dawn

Credits to laconic2. Received on Fri Oct 01 2004 - 01:52:54 CEST

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