Database management systems have become ubiquitous as a fundamental tool for managing information, and a course on the principles and practice of database systems is now an integral part of computer science curricula. This book covers the fundamentals of modern database management systems, in particular relational database systems. It is intended as a text for an introductory database course for undergraduates, and we have attempted to present the material in a clear, simple style. A quantitative approach is used throughout and detailed examples abound. An extensive set of exercises (for which solutions are available online to instructors) accompanies each chapter and reinforces students' ability to apply the concepts to real problems. The book contains enough material to support a second course, ideally supplemented by selected research papers. It can be used, with the accompanying software and SQL programming assignments.