Relational Theory for Computer Professionals

Chapter 1. Basic Database Concepts

Our life is frittered away by detail ... Simplify, simplify.

—Henry David Thoreau: Walden (1854)

This introductory chapter is just meant to provide “the view from 30,000 feet,” as it were. It’s deliberately not deep, and if you do already know something about database management you probably won’t find anything here you don’t already know. But I think it’s worth your while to give the material a “once over lightly” reading anyway, if only to get a sense of what background knowledge I’ll be assuming and relying on in subsequent chapters. Also, the chapter introduces the running example, which you’ll definitely need to be familiar with when we get to those later chapters.

What’s a database?

A database can be thought of as a kind of electronic filing cabinet; it contains digitized information (“data”), which is kept in persistent storage of some kind, typically on magnetic disks. Users can insert new information into the database, and delete, change, or retrieve existing information in the database, by issuing requests or commands to the software that manages the database—which is to say, the database management system (DBMS for short). Note: Throughout this book, I take the term user to mean either an application programmer or an interactive user^[2] or both, as the context demands.

Now, in practice, those user requests to the DBMS can be formulated in a variety of different ways (e.g., by pointing and clicking with a mouse). For our purposes, however, ...