Relational Theory for Computer Professionals

Chapter 10. SQL Tables

[The] natural sequel of an unnatural beginning

—Jane Austen: Persuasion (1818)

Recall from Chapter 1 that my plan for this book (for Parts I and III, at least) looked like this:

• First, I wanted to explain the relational model as such, using a language expressly designed for that purpose called Tutorial D.

• Then I wanted to show how terms and concepts from the relational model are realized in concrete form in the SQL language specifically.^[78] (Please note, therefore, that I’m not trying to cover the whole of SQL in this book; rather, I just want to cover what might be called the relational aspects—what I referred to in the preface as the core features—of that language.)

I also claimed in Chapter 1 that, precisely because of the foregoing plan, this book wasn’t going to look much like most of the books and presentations currently available in the marketplace that purport to be an introduction to relational databases. What’s more, I don’t think the chapters in this part of the book are going to look much like the usual introductory books and presentations on SQL either, come to that.

Incidentally, I do believe that learning the relational model first and SQL second is much easier than doing it the other way around. Part of the reason for this state of affairs is that doing it the other way around typically requires rather a lot of unlearning (and as I said in the preface, unlearning can be very difficult, as we all know).

A little history

The SQL language was originally ...