Orchid XP v8 wrote:
>>> As I understand it, this is considered one of the "seminal texts" on 
>>> relational databases. 
>>
>> It was some 25 years ago too. :-)
> 
> OK, so the book I'm worshiping is a little out of date.

No. That's my point. It's so seminal that it hasn't needed to be replaced in 
25 years either.

> Heh... you see what I just did there? :-D

> Well, I recall a piece complaining that SQL doesn't actually follow the 
> relational model very closely. (E.g., you can write querires where the 
> ordering of colums matters. You can't treat derived relations in the 
> same way as base relations. etc.) They emplored vendors to add the 
> missing features, and generally close the gap.

Yes. And you can have duplicate rows in your results, and so on. But that's 
just practicality.

My understanding is that the calculus describes "this is the result I want", 
while the algebra is "follow these steps".  Of course, the steps don't have 
to be followed in order in the algebra (associative, commutitive, etc), so 
that's OK.

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

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