By Paul Litwin
This paper was part of a presentation at a Microsoft TechEd conference in the mid-1990s. It was adapted from Microsoft Access 2 Developer's Handbook, Sybex 1994, by Ken Getz, Paul Litwin and Greg Reddick. Reprinted with permission of the publisher. While the paper uses Microsoft Access (version 2) for the examples, the vast majority of the discussion applies to any database and holds up pretty well over 11 years after it was written. Overview
Database design theory is a topic that many people avoid learning for lack of time. Many others attempt to learn it, but give up because of the dry, academic treatment it is usually given by most authors and teachers. But if creating databases is part of your job, then you're treading on thin ice if you don't have a good solid understanding of relational database design theory. This article begins with an introduction to relational database design theory, including a discussion of keys, relationships, integrity rules, and the often-dreaded "Normal Forms." Following the theory, I present a practical step-by-step approach to good database design. The Relational Model
The relational database model was conceived by E. F. Codd in 1969, then a researcher at IBM. The model is based on branches of mathematics called set theory and predicate logic. The basic idea behind the relational model is that a database consists of a series of unordered tables (or relations) that can be manipulated using non-procedural operations that return tables. This model was in vast contrast to the more traditional database theories of the time that were much more complicated, less flexible and dependent on the physical storage methods of the data. Note: It is commonly thought that the word relational in the relational model comes from the fact that you relate together tables in a relational database. Although this is a convenient way to think of the term, it's not accurate. Instead, the word...