Refactoring SQL Applications

Preface

Ma, sendo l’intento mio scrivere cosa utile a chi la intende, mi è parso più conveniente andare drieto alla verità effettuale della cosa, che alla immaginazione di essa.

But, it being my intention to write a thing which shall be useful to him who apprehends it, it appears to me more appropriate to follow up the real truth of a matter than the imagination of it.

—Niccolò Machiavelli

Il Principe, XV

THERE IS A STORY BEHIND THIS BOOK. I HAD HARDLY FINISHED THE ART OF SQL, WHICH WASN’T ON sale yet, when my then editor, Jonathan Gennick, raised the idea of writing a book about SQL refactoring. SQL, I knew. But I had never heard about refactoring. I Googled the word. In a famous play by Molière, a wealthy but little-educated man who takes lessons in his mature years marvels when he discovers that he has been speaking “prose” for all his life. Like Monsieur Jourdain, I discovered that I had been refactoring SQL code for years without even knowing it—performance analysis for my customers led quite naturally to improving code through small, incremental changes that didn’t alter program behavior. It is one thing to try to design a database as best as you can, and to lay out an architecture and programs that access this database efficiently. It is another matter to try to get the best performance from systems that were not necessarily well designed from the start, or which have grown out of control over the years but that you have to live with. And there was something appealing in the ...