Re: Foreign key in Oracle Sql

From: DA Morgan <damorgan_at_x.washington.edu>
Date: Fri, 21 Jan 2005 23:20:17 -0800
Message-ID: <41f1fea7$1_2@127.0.0.1>

pc wrote:

> DA Morgan wrote:
>
>

>> ... How could a table, in
>> advance, know the cardinality of the data that will be loaded into it?

>
>
> that's not the question, rather it is why shouldn't the dbms always
> (don't worry about knowing 'in advance') know the cardinality and then
> choose what to do about it!

You really need to take a basic database class. I can't teach you a college class on this subject in a usenet group. But simply ... all databases have optimizers ... optimizers make different choices based on the data, its cardinality, is skew, and many other factors including the number of table and index blocks that may or may not be cached in memory and the percentage of rows anticipated to be read as well as numerous other factors.

Your question is at the level of I want to be a brain surgeon. Why do I have to know anything about synapses when the tools I'm used to working with are a rusty knife and a drill I pickup up used at a yard sale.

>> Perhaps a crystal ball? Or how about data skew? A built in Ouija board
>> function? ... Taro cards?

>
> these don't sound like computer techniques to me.

Sorry but based on what you demonstrated I'm not sure you'd recognize one if it fell on you.

>> Some day you'll get exactly what you want. No doubt Microsoft will sell
>> it to the same people that currently think MS Access is a database.

>
> apologies, i thought you had been touting Oracle.

Reread what I wrote. Try again.

>> And
>> it will perform as abysmally as all similar products do and be relegated
>> to being the butt of jokes.

>
> agree, they're all abysmal if one believes missed function is as much
> poor performance as silly function done well.

Nonsense. Several of them are absolutely brilliant.

> eg. right now, the industry is spending a lot of effort and otherwise to
> try to model unknown knowledge, some with Nulls and some with Objects. i
> hardly think we are ready for pedantry when the state of the art is so
> immature (ie. when even the basic questions haven't been posed coherently).
>
> p

What is immature is your actual knowledge of the subject. When you get done posturing I suggest you enroll at a local college and actually take a computer science class.

-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)

Received on Sat Jan 22 2005 - 01:20:17 CST