Learning SQL, 3rd Edition

Chapter 1. A Little Background

Before we roll up our sleeves and get to work, it would be helpful to survey the history of database technology in order to better understand how relational databases and the SQL language evolved. Therefore, I’d like to start by introducing some basic database concepts and looking at the history of computerized data storage and retrieval.

Note

For those readers anxious to start writing queries, feel free to skip ahead to Chapter 3, but I recommend returning later to the first two chapters in order to better understand the history and utility of the SQL language.

Introduction to Databases

A database is nothing more than a set of related information. A telephone book, for example, is a database of the names, phone numbers, and addresses of all people living in a particular region. While a telephone book is certainly a ubiquitous and frequently used database, it suffers from the following:

• Finding a person’s telephone number can be time consuming, especially if the telephone book contains a large number of entries.

• A telephone book is indexed only by last/first names, so finding the names of the people living at a particular address, while possible in theory, is not a practical use for this database.

• From the moment the telephone book is printed, the information becomes less and less accurate as people move into or out of a region, change their telephone numbers, or move to another location within the same region.

The same drawbacks attributed ...