Section 1.13. The Completed Plans

1.13. The Completed Plans

We have reviewed the basic foundations for laying plans in constructing a database system. We have reviewed the fundamentals of data modeling , and in particular the broad steps involved in normalizing data to third normal form. We have then proceeded to review a number of scenarios, in which a faulty design can be identified as the road to disaster.

Most examples in this chapter come directly from or are inspired by cases I have encountered in some big companies. And it is always striking to consider how much energy and intelligence can be wasted trying to solve performance problems that are born from the ignorance of elementary design principles. Such performance issues need not be present, yet they are quite common and often made worse by further denormalization of what is already a questionable design, on the unassailable grounds of "performance improvement." One query may, in fact, run much faster, but unfortunately, the nightly batch program now takes twice as long. In this way, and almost without being noticed, a full information system is built on a foundation of sand.

Successful data modeling is the disciplined application of what are, fundamentally, simple design principles.