December 2014
Intermediate to advanced
852 pages
17h 57m
English
Content preview from Joe Celko's SQL for Smarties, 5th EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 4
Keys, Locators, and Generated Values
Abstract
Tables used logical keys to locate data as opposed to pointers and other physical devices. I discuss my classification system for keys.
Keywords
Keys
Locators
Generated values
Compound key
IDENTITY
Natural key
Artificial key
Exposed physical locator
Surrogate key
GUID
Denormalization
Donald Knuth
Key is an unfortunate term in IT. We have encryption keys, sort keys, access keys, and probably a dozen other uses for the term I cannot think of right now. Unless I explicitly say otherwise, I will mean a relational key in this book. A (relational) key is a subset of one or more columns in a table which are guaranteed unique for all possible rows. If there is more than one column in the subset, this is a compound ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.