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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