This project started at the end of the summer in 2005, and due to unfortunate circumstances took much longer than originally planned. My coauthor was already diagnosed when he contacted me to jointly write a book “about the mathematics in our profession.” We started writing in October 2005 and first spent a lot of time together developing the example database design—especially the involved data integrity constraints—that would be used throughout the book. “I’ll start at the beginning, you start at the end, then we will meet somewhere in the middle,” is what he said once the database design was finished. In the months that followed Lex put in a big effort to create the Introduction through Chapter 3. Unfortunately, around Christmas 2005 his situation deteriorated rapidly and he never saw the rest of this book.

Thankfully, I received the support of many other people to complete this project.

The contribution of my main reviewers to the quality of this book has been immense. I’d like to thank Chris Date, Cary Millsap, Hugh Darwen, and Frans Remmen for their efforts in reviewing the manuscript and offering me many comments and suggestions to improve the book.

I also greatly appreciate the time some of my colleagues at Centraal Boekhuis put into this book: Jaap de Klerk, Lotte van den Hoek, and Emiel van Bockel for reviewing several chapters; Petra van der Craats for helping me out when I was struggling with the English language; and Ronald Janssen for his overall support for this project.

I must mention the support I received from the people at Apress, especially my editor Jonathan Gennick for remaining committed to this book even when the original plan had to be completely revised, and the other people at Apress involved in the production of this book—the only ones I’ve never met in person: Tracy Brown Collins, Tina Nielsen, Susannah Davidson Pfalzer, Kelly Winquist, and April Eddy.

I would like to mention a few other people: Mogens Nørgaard, for his support early in 2006 in the time right after Lex’s passing; Juliette Nuijten, for her continued support of this project; and Bert de Brock, for the influential curriculum on database systems he provided together with Frans Remmen more than 20 years ago. Without those courses this book would not exist.

I must of course also thank my wife for giving me the opportunity to embark upon this project and to finish it, and our kids for their patience, especially these last three months; I had to promise them not even to think about writing another book.

And finally, I thank Lex, who initiated this book and decided to contact me as his coauthor.

Well Lex, we finally did it, your last project is done.

Toon Koppelaars
Zaltbommel, the Netherlands, March 2007