This book provides a comprehensive treatise on the use of fuzzy sets, fuzzy logic, and possibility theory for dealing with imprecise and vague information in database management systems. First, general issues related to vague and imprecise data are discussed. Next, fuzzy and possibilistic extensions of data models and database architectures are presented. Second, the use of fuzzy sets, fuzzy logic and possibility theory in information retrieval and querying to attain more flexible and "human-consistent" querying capabilities is discussed. Theoretical works and implemented systems for commercial database management systems are discussed. A fuzzy approach to database security is considered. The particular articles are written by leading authorities from all over the world.