NULL
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