1.1 Introduction

Since we published the first edition of this book, based on Oracle 8 i, we've witnessed the rise and fall of the dot-coms and followed the ups and downs of the NASDAQ. We've seen URLs become part of our everyday vocabulary and are exchanging e-mail with just about everyone we know. We changed the way we conduct business and now can buy or sell most anything we want on the Web. We can find old friends, the nearest pet store, what's playing at the movies, or a good restaurant. We are always reachable via our wireless cell phones and take notes on our PDAs. We never get lost when we've got a GPS to guide us. We use self-service applications both at work and home. We can transfer money from one account to another with the click of a mouse and no longer have worry about making it to the bank during business hours or the security of being at an ATM at night.

What's behind this technology? Almost always there's a database to organize and store the data, and often there's a data warehouse used in the strategic decision-making process of the business.

1.2 What is a data warehouse?

The data warehouse is a database containing data from multiple operational systems that has been integrated, aggregated, and structured so that it can be used to support the analysis and decision-making process of a business.