SQL Bible, Second Edition

Chapter 1. SQL and Relational Database Management Systems

Information may be the most valuable commodity in the modern world. It can take many different forms — such as accounting and payroll information, information about customers and orders, scientific and statistical data, graphics, or multimedia. We are virtually swamped with data, and we cannot — or at least we'd like to think about it this way — afford to lose it. These days we simply have too much data to keep storing it in file cabinets or cardboard boxes. The need to store large collections of persistent data safely, "slice and dice" it efficiently from different angles by multiple users, and update it easily when necessary is critical for every enterprise. That need mandates the existence of databases, which accomplish all the tasks listed, and then some. To put it simply, a database is just an organized collection of information — with emphasis on "organized."

A more specific definition often used as a synonym for "database" is database management system (DBMS). That term is wider and, in addition to the stored information, includes some methods to work with data and tools to maintain it.

Note

DBMS can be defined as a collection of interrelated data plus a set of programs to access, modify, and maintain the data. More about DBMS later in this chapter.

Desirable Database Characteristics

There are many differing ideas about what a database is and what it should do. Nevertheless, all modern databases should have at least the ...