From: Mike Stephens <rubfor@...>
Date: 2010-11-19T23:06:44+09:00
Subject: Re: Where to start from?

Phillip Gawlowski wrote in post #962566:
> > 3) SQL's JOIN (set theory).
> What's the intersection of the sets {1,2,3,5,6} and {1,2,4,6}?

The original motivation of the N-ary Relational Model (ie the invention
of Codd and Date and the one we know today) was (as ever)
there is far more to do than can be done by the number of trained
programmers available. The model was to allow non-IT professionals to
manipulate organisational data without unnecessary spec!alist knowledge.
This is why relational databases first appeared as sort of warehouse
copies of data also held on more traditional arcane data storage
systems.

Although the first relational languages (like DSL) were rather
mathematical, the underlying principle was that you only need to
understand a few high-level powerful concepts. Quickly we got to such
things as Sequel (not to be confused with SQL). Sequel is 'structured
english query language'(and a play on the name of an earlier language
QUEL).

I therefore take issue with your point that you need to know maths set
theory to appreciate SQL. It was designed to be simple to understand
without a spec!alist background.

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