Should you be interested in pursuing an in-depth study of database technology, here are my recommendations for books on this subject. I've chosen these particular books because they have stood the test of time and have become standard reading within the database industry and academic institutions. (I'm pleased to state that my book has become part of this notable list.) Keep in mind that most of these books are going to be challenging to read; the authors presume that you have a fair amount of background in computers and programming or are pursuing a degree in computer science.
Codd, E. F. (1990). The Relational Model for Database Management: Version 2. Reading, MA: Addison-Wesley. (Note: This book is hard to find, but it's worth having in your library if you're going to become a serious database developer.)
Connolly, Thomas, and Carolyn Begg. (2002). Database SystemsA Practical Approach to Design, Implementation, and Management, Third Edition. Boston, MA: Addison-Wesley.
Date, C. J. (2000). An Introduction to Database Systems, Seventh Edition. Boston, MA: Addison-Wesley.
. (2000). The Database Relational ModelA Retrospective Review and Analysis. Boston, MA: Addison-Wesley.
Date, C. J., and Hugh Darwen. (2000). Foundation for Future Database SystemsThe Third Manifesto, Second Edition. Boston, MA: Addison-Wesley.
Fleming, Candace C., and Barbara von Halle. (1989). Handbook of Relational Database Design. Reading, MA: Addison-Wesley.
Hoffer, Jefferey A., Mary B. Prescott, and Fred R. McFadden. (2002). Modern Database Management, Sixth Edition. Upper Saddle River, NJ: Prentice Hall.
Kroenke, David M. (2000). Database ProcessingFundamentals, Design, & Design, Seventh Edition. Upper Saddle River, NJ: Prentice Hall.
I do recommend other books on a variety of subjects, such as database design and theory, data modeling, GUI design, SQL, Visual Basic, and .NET. You can review these recommendations by accessing my Web site at http://www.ForMereMortals.com.