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Elementary Key Attributes


Elementary Key Attributes

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paul s-306273
paul s-306273
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I notice that we are now up to approimately 25% correct.

How on earth did that happen?
TomThomson
TomThomson
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paul s-306273 (10/12/2011)
I notice that we are now up to approimately 25% correct.

How on earth did that happen?


I think John Arnott already answered that question in this post.

Tom

Tom Brown
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I think that volcanic air is getting to you Tom, This question is way over most of our heads - a really hard question. No amount of googling seemed able to turn up any clues. And... well, once you see the answer its no easier to work it out.

I got the not null part. And its probably not the primary key, (otherwise why call it an elementary key). The middle one long complex answer I chose this because it was long and complex - don't pretent to understand it even now, and random choice for the other one.
TomThomson
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Tom Brown (12/8/2011)
I think that volcanic air is getting to you Tom, This question is way over most of our heads - a really hard question. No amount of googling seemed able to turn up any clues. And... well, once you see the answer its no easier to work it out.

I got the not null part. And its probably not the primary key, (otherwise why call it an elementary key). The middle one long complex answer I chose this because it was long and complex - don't pretent to understand it even now, and random choice for the other one.

I probably overestimated how much relational theory people would be familiar with, and put the question into a form that was harder than it could have been if presented in a different form. Multiple choice questions where you have to select several answers are inherently more difficult than multiple choice questions where you select only one answer (choosing 3 out of five means choosing one combination out of 10 possible combinations, choosing 1 out of five is easier than choosing 1 out of 10).

I'm surprised that googling came up with nothing, though - it finds the Halpin,Morgan and Morgan book, Joe Celko's book, the Wikipedia normalisation article, Zaniolo's paper, and Scot Becker's rather silly (he parades his ignorance of why EKNF is important) paper on normalisation (Google gives a broken link to that one, but it's there in the cache - at least it is today) all on the first page of results when I try it - but maybe Google knows I'm interested in normalisation.

Tom

Tom Brown
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Yes I found the Wiki, and other articles, but the whole topic of normalisation seems couched in academic terms.

I was trying to google for simple definitions of things like elemetary attribute key or prime attribute key - definitions that don't refer to other similar terms, sending my round in circles of cyclic definitions. I've since read your 3 normalisation articles, and heard mention that you may be planning a 4th. Perhaps you could have a bash at some good practical definitions of the terms used in normalisation - as a kind of 'demistification' level zero article. I'm sure there is something simple I'm not getting in normalisation, however here are my 'simple' definitions (which may be wrong)

Attribute: This is any piece of data. In 1NF equates to a column
Attribute Key: a piece of data that on its own, or when combined with other attributes could uniquely identify a row.
Candidate Key: any column, or combination of columns in 1NF that would uniquely identify a Row
Primary Attribute Key: A single column candidate key
Elementary Attribute Key: ~ still unsure about this one.
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