Database Design and Relational Theory: 
Because databases often stay in production for decades, careful design is critical to making the database serve the needs of your users over years, and to avoid subtle errors or performance problems. In this book, CJ Date, a leading exponent of relational databases, lays out the principles of good database design. Database Design and Relational Theory investigates denormalization, implicit dependencies, redundancy, and many other topics.
got it on 2012-07-29.