Invisible wrote:
> One of the points of a relational database is that several programs can 
> use the data, possibly in ways not originally envisaged.

I'd go so far as to say that was the *primary* point. We already had 
standard database stuff using pointers, called CODASYL. It sucked if you 
wanted to do anything unexpected with it.

> Today, lots and lots of people seem to forget this. They think of a 
> database as being a system for holding data that only one application 
> uses and only that application understands. This isn't what a database 
> is supposed to be. It's supposed to facilitate access by multiple programs.

This si why I laugh at people who say it's better to put the data 
consistency assurances in the program.

> Or sometimes it's just for performance. An order can be completely 
> identified by the customer it's for, the date it was placed, and what 
> was ordered. 

Well, probably customer and timestamp. You don't have to know what they 
ordered at 14:01 on Jan 23 to find it. The artificial key, being artificial, 
is a secondary key, not a primary key.  Unless it is printed on the physical 
slip you used to take the order, like at a restaurant or something.

-- 
Darren New, San Diego CA, USA (PST)
   The question in today's corporate environment is not
   so much "what color is your parachute?" as it is
   "what color is your nose?"

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