This book developed from course notes used in Stanford's CS145 introduction to databases. CS145 is the first in a sequence of five courses.1 As taught originally by Arthur Keller, it evolved into a course that stresses the aspects of database systems of most use to the majority of computer science students: database design and programming. The course also involves an extensive, running project, in which the students design and then implement a substantial database application. Assignments related to this project, other homework assignments, exams, and other course materials are available from this book's home page; see the section on "Support on the World Wide Web."