9This book is intended as a text for an introductory course in database systems. It presents the elementary concepts and describes the basic concepts and functions of databases.We show how to use SQL to create, query and update a database.We include coverage of data modelling using UML and ODL notations in addition to the more traditional E/R diagrams and cover basic design theory, including normal forms, referential integrity, security and the use of transactions to maintain database integrity.