Cover Page

The Kimball Group Reader

Relentlessly Practical Tools for Data Warehousing and Business Intelligence

Remastered Collection

Ralph Kimball and Margy Ross
with Bob Becker, Joy Mundy, and Warren Thornthwaite


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About the Authors

Ralph Kimball founded the Kimball Group. Since the mid-1980s, he has been the DW/BI industry's thought leader on the dimensional approach and has trained more than 20,000 IT professionals. Prior to working at Metaphor and founding Red Brick Systems, Ralph co-invented the Star workstation at Xerox's Palo Alto Research Center (PARC). Ralph has a Ph.D. in Electrical Engineering from Stanford University.

Margy Ross is President of the Kimball Group and Decision Works Consulting. She has focused exclusively on data warehousing and business intelligence since 1982. Margy has consulted with hundreds of clients and taught DW/BI best practices to tens of thousands. Prior to working at Metaphor and co-founding DecisionWorks Consulting, she graduated with a B.S. in Industrial Engineering from Northwestern University.


Project Editor

Tom Dinse

Production Editor

Christine O'Connor

Copy Editor

Kim Cofer

Manager of Content Development & Assembly

Mary Beth Wakefield

Marketing Director

David Mayhew

Marketing Manager

Carrie Sherrill

Professional Technology & Strategy Director

Barry Pruett

Business Manager

Amy Knies

Associate Publisher

Jim Minatel

Project Coordinator, Cover

Brent Savage


Nancy Carrasco


Johnna VanHoose Dinse

Cover Designer


Cover Image

The Kimball Group

Warren Thornthwaite (1957–2014)

The Kimball Group lost Warren to a brain tumor in 2014. He wrote many insightful articles that appear in this Reader. All of us at the Kimball Group miss Warren dearly—his intellect, curiosity, creativity, and most especially, his friendship and sense of humor. As any of you who met Warren will attest, he was truly one of a kind!


First, we want to thank the 33,000 subscribers to the Kimball Design Tips, and the uncounted numbers who have visited the Kimball Group website to peruse our archive. This book brings the remastered Design Tips and articles together in what we hope is a very usable form.

The Kimball Group Reader would not exist without the assistance of our business partners. Kimball Group members Bob Becker, Joy Mundy, and Warren Thornthwaite wrote many of the valuable articles and Design Tips included in the book. Thanks to Julie Kimball for her insightful comments. Thanks also to former Kimball Group member Bill Schmarzo for his contributions on analytic applications.

Thanks to our clients and students who have embraced, practiced, and validated the Kimball methods with us. We have learned as much from you as you have from us!

Jim Minatel, our executive editor at Wiley Publishing, project editor Tom Dinse, and the rest of the Wiley team have supported this project with skill, encouragement, and enthusiasm. It has been a pleasure to work with them.

To our families, thank you for your support over the twenty year span during which we wrote these Design Tips and articles. Julie Kimball and Scott Ross: We couldn't have done it without you! And, of course, thanks to our children, Sara Kimball Smith, Brian Kimball, and Katie Ross, who have grown into adults over the same time!


The Kimball Group's article and Design Tip archive has been the most popular destination on our website ( Stretching back twenty years to Ralph's original 1995 DBMS magazine articles, the archive explores more than 250 topics, sometimes in more depth than provided by our books or courses.

With The Kimball Group Reader, Second Edition, we have organized all of the articles in a coherent way. But The Reader is more than merely a collection of our past magazine articles and Design Tips verbatim. We have trimmed the redundancy, made sure all the articles are written with the same consistent vocabulary, and updated many of the figures. This is a new and improved remastered compilation of our writings.

After considerable discussion, we decided to update many time references and edit content throughout the book to provide the perspective of 2015 rather than leaving old dates or outdated concepts in the articles. Thus an article written in 2007 may use 2015 in an example! When articles refer to the number of years that have passed, we have updated these references relative to 2015. For example, if a 2005 article originally said “during the past five years,” the article now reads “during the past fifteen years.” Mentions regarding our years of experience, number of books sold, articles written, or students taught have also been updated to 2015 figures. Finally, we occasionally changed references from outmoded technologies such as “modems” to more modern technologies, especially “internet.” We trust these changes will not mislead or cause confusion, but rather make your reading experience more natural.

Intended Audience and Goals

The primary reader of this book should be the analyst, designer, modeler, or manager who is delivering a data warehouse in support of business intelligence. The articles in this book trace the entire lifecycle of DW/BI system development, from original business requirements gathering all the way to final deployment. We believe that this collection of articles serves as a superb reference-in-depth for literally hundreds of issues and situations that arise in the development of a DW/BI system.

The articles range from a managerial focus to a highly technical focus, although in all cases, the tone of the articles strives to be educational. These articles have been accessed thousands of times per day on the Kimball Group website over a span of 20 years, so we're confident they're useful. This book adds significant value by organizing the archive, and systematically editing the articles to ensure their consistency and relevance.

Preview of Contents

Following two introductory chapters, the book's organization will look somewhat familiar to readers of The Data Warehouse Lifecycle Toolkit, Second Edition (Wiley, 2008) because we've organized the articles topically to correspond with the major milestones of a data warehouse/business intelligence (DW/BI) implementation. Not surprisingly given the word “Kimball” is practically synonymous with dimensional modeling, much of The Reader focuses on that topic in particular.

Navigation Aids

Given the breadth and depth of the articles in The Kimball Group Reader, we have very deliberately identified over two dozen articles as “Kimball Classics” because they captured a concept so effectively that we, and many others in the industry, have referred to these articles repeatedly over the past twenty years. The classic articles are designated with a special icon that looks like this:


We expect most people will read the articles in somewhat random order, rather than digesting the book from front to back. Therefore, we have put special emphasis on The Reader's index as we anticipate many of you will delve in by searching the index for a particular technique or modeling situation.

Terminology Notes

We are very proud that the vocabulary established by Ralph has been so durable and broadly adopted. Kimball “marker words” including dimensions, facts, slowly changing dimensions, surrogate keys, fact table grains, factless fact tables, and degenerate dimensions, have been used consistently across the industry for more than twenty years. But in spite of our best intentions, a few terms have morphed since their introduction; we have retroactively replaced the old terms with the accepted current ones.

Since most people won't read this book from cover to cover, we need to introduce some common abbreviations up front: