What is everywhere but occupies no space; can be measured but not seen or touched; can be spent, wasted, or killed, but not destroyed or changed? The simple answer is time, and the relationship between the fourth dimension and data is the foundation for Developing Time-Oriented Database Applications in SQL, a fascinating book by Richard T. Snodgrass.

Anyone who has ever attempted to create or modify a database containing temporal data will appreciate the complexity of the task. Snodgrass's book aims to simplify it by first helping the reader fully understand the concepts involved before covering the SQL code needed to carry out the work. The book is punctuated with interesting information about the measurement of time through the ages, plus illustrative examples of where disaster has occurred following the misuse of time-specific data, and it comes with a free CD-ROM containing example code.

Make no mistake, this book is by no means an easy read. It's complex and very wordy, and non-programmers may get lost in the SQL quite quickly. This aside, it's an informative, well-written attempt to explain a complicated concept. --Steve Russell, amazon.co.uk