Re: Useful Oracle books - C.J. Date theory vs. practicality

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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