July 2002
Beginner
424 pages
9h 30m
English
Content preview from SQL: Visual QuickStart Guide
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Chapter 3. SQL Basics
You may have noticed that I barely mentioned SQL in the preceding chapter. Remember this equation:
SQL ≠ Relational model
SQL is based on the relational model but isn’t a faithful implementation of it. One departure from the model is that in SQL, primary keys are optional rather than mandatory. Consequently, tables without keys may have duplicate rows, rendering some data inaccessible. A complete review of the disparities is beyond the scope of this book (if you want to learn more, search the Web for SQL articles by E.F. Codd, Chris Date, or Fabian Pascal). The upshot of these discrepancies is that DBMS users, and not the DBMS itself, bear the responsibility for enforcing a relational structure. Another result is that the ...
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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.