This book provides improved and extensive coverage of concepts, database system internals and new tools and techniques. It is intended for a first course in databases at the junior or senior undergraduate, or first-year graduate level, and offers a complete background in the basics of database design, languages and system implementations. Concepts are presented using intuitive descriptions, and important theoretical results are covered, but formal proofs are omitted. The concepts and algorithms covered are based on those used in existing commercial or experimental database systems, and are presented in a general setting that is not tied to one particular database system.