This book is about parallel database techniques, written by experts in the field. It aims to help designers and users of large databases understand how software and hardware can handle parallel database management systems. The book is divided into three main parts: Request manager, Parallel machine architecture, and Partitioned Data Store. Parallelism in databases, especially relational data models, is achieved through independence between tables and tuples. The book discusses parallel query optimization techniques and a new approach to parallel join using the XPRS shared memory parallel database system.