SQL and Relational Theory

Chapter 1. Setting the Scene

ARELATIONAL APPROACH TO SQL: THAT’S THE THEME, OR ONE OF THE THEMES, OF THIS BOOK. Of course, to treat such a topic adequately, I need to cover relational issues as well as issues of SQL per se—and while this remark obviously applies to the book as a whole, it applies to this first chapter with special force. As a consequence, this chapter has comparatively little to say about SQL as such. What I want to do is review material that for the most part, at any rate, I hope you already know. My intent is to establish a point of departure: in other words, to lay some groundwork on which the rest of the book can build. But even though I hope you’re familiar with most of what I have to say in this chapter, I’d like to suggest, respectfully, that you not skip it. You need to know what you need to know (if you see what I mean); in particular, you need to be sure you have the prerequisites needed to understand the material to come in later chapters. In fact I’d like to recommend, politely, that throughout the book you not skip the discussion of some topic just because you think you’re familiar with that topic already. For example, are you absolutely sure you know what a key is, in relational terms? Or a join?^[2]

The Relational Model Is Much Misunderstood

Professionals in any discipline need to know the foundations of their field. So if you’re a database professional, you need to know the relational model, because the relational model is the foundation (or a huge ...