Re: Useful Oracle books - C.J. Date theory vs. practicality
- From: Mladen Gogala <mladen@xxxxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 28 May 2004 16:13:28 -0400
On 05/28/2004 03:43:04 PM, Lex de Haan wrote:
> Hi Jared,
>
> the difference becomes apparent if you try a condition like the following:
>
> 'Mort Subite' = NULL
>
> This condition is neither TRUE nor FALSE; it evaluates to UNKNOWN.
>
> According to three-valued logic, NOT UNKNOWN evaluates to UNKNOWN;
> therefore, both statements will execute their ELSE branch;
> so the first one executes statement 2, and the second one executes statement
> 1.
>
> My math teacher (many moons ago) usually would say at this point: QED.
Lex, with all due respect, you are playing devil's advocate in the debate that
is
completely analogous to the debate among mathematicians whether there should be
zero
or not. NULL understood as an absence of value is very practical and
substituting
default value for the logical purity is the same thing as inventing the value of
'PIMP' to which all singles would be related (your example). The example with
the
number zero is not chosen accidentally, it, too , introduced new concepts of
"infinity" and "undefined" into mathematics. Same as the origin of NULL, the
origin
of zero is a nebulous subject. The Babylonians were known to have used a space
as a
placeholder for empty "columns" as far back as 1700 BC. Around 1400 years
later,
they developed the first known symbol to stand for an empty place. It looked
something
like YY. It didn't actually stand for the number we know as "zero." It was
never used
alone. It was only a place holder. The Mayan culture developed a symbol for the
number
zero, probably independently of the Babylonians, sometime later. So did the
Hindu culture.
The first records we have of the symbol we use for 0, is from Hindu writings
from the late
9th century. There was no internet back then, but information still got around.
Mostly by
camelback, or foot, so it took awhile for 0 to migrate to Arab lands, (probably
due to commerce).
Eventually, about 400 years after South Asia and Asia Minor had been using 0
and inventing
and discovering math concepts the we in the west couldn't even consider
(because we were
busy being "religiously enlightened" and culturally superior) 0 finally got to
the civilized
world. In its superior intellect, civilized Europe continued to use the Roman
numeral
system, refusing to change for as long as possible, as the infidels ran circles
around it.
Eventually the Europeans gave in. It is very comforting to know that the
concept of NULL
didn't need that long to gain acceptance. Predictably, once again, the
resistance comes
from Europe....
As for COBOL, it has no logic whatsoever. It stands for "Completely Outdated,
Badly
Overused Language". I started my career as a junior COBOL programmer, so I know.
PS:
---
I was born and raised in Croatia, which is in Europe, but not quite.
--
Mladen Gogala
Oracle DBA
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