Relational Database Writings 1991 1994

Readers familiar with the three prior volumes of database guru Chris Date's Relational Database Writings series will need no further recommendation. The fourth volume compiles Date's authoritative columns, articles, and papers on various aspects of relational technology--spanning the years 1991 to 1994.

A review of relational concepts -- An overview of Tutorial D -- Time and the database -- What is the problem? -- Intervals -- Operators on intervals -- The EXPAND and COLLAPSE operators -- The PACK and UNPACK operators -- Generalizing the relational operators -- Database design -- Integrity constraints 1 : candidate keys and related constraints -- Integrity constraints 2 : general constraints -- Database queries -- Database updates -- Stated times and logged times -- Point and interval types revisited.

Along with its companion volume (Database Dreaming Volume I), this book offers a collection of essays on the general topic of relational databases and relational database technology. Most of those essays, though not all, have been published before, but only in journals and magazines that are now hard to find or in books that are now out of print. Here’s a lightly edited excerpt from the preface (so this is the author speaking): I went back and reviewed all of those early essays, looking for ones that seemed worth reviving (or, rather, revising and reviving) at this time. Of course, some of them definitely weren’t! However, out of a total of around 130 original papers, I did find some 20 or so that seemed to me worth preserving and hadn’t already been incorporated in, or superseded by, more recent books of mine. So I tracked down the original versions of those 20 or so papers and set to work. When I was done, though, I found I had somewhere in excess of 600 pages on my hands—too much, in my view, for just one book, and so I split them across two separate volumes. Highlights of the present volume include a detailed explanation of the multiple assignment operator and why it’s so essential; an investigation into why object and database technologies are so much more different than they’re often made out to be; a critical examination of SQL’s support for pointers (“references”); a tutorial on the counterintuitive (but crucial) concept of tables with no columns; and an annotated and extended debate between the author and E. F. Codd, inventor of the relational model, on the subject of nulls and three-valued logic.

Fifty years of relational. It’s hard to believe the relational model has been around now for over half a century! But it has—it was born on August 19th, 1969, when Codd’s first database paper was published. And Chris Date has been involved with it for almost the whole of that time, working closely with Codd for many years and publishing the very first, and definitive, book on the subject in 1975. In this book’s title essay, Chris offers his own unique perspective (two chapters) on those fifty years. No database professional can afford to miss this one of a kind history. But there’s more to this book than just a little personal history. Another unique feature is an extensive and in depth discussion (nine chapters) of a variety of frequently asked questions on relational matters, covering such topics as mathematics and the relational model; relational algebra; predicates; relation valued attributes; keys and normalization; missing information; and the SQL language. Another part of the book offers detailed responses to critics (four chapters). Finally, the book also contains the text of several recent interviews with Chris Date, covering such matters as RM/V2, XML, NoSQL, The Third Manifesto, and how SQL came to dominate the database landscape.

This book is a revised, upgraded, and hugely improved version of an earlier one called Logic and Databases. Although it’s effectively a brand new book, therefore, the following remarks from that earlier book are still relevant here. First, logic and databases are inextricably intertwined. The relational model itself is essentially just elementary logic, tailored to database needs. Now, if you’re a database professional, this won’t be news to you—but you still might not realize just how much everything we do in the database world is (or should be!) affected by logic. Logic is fundamental, and everywhere. As a database professional, therefore, you owe it to yourself to understand the basics of formal logic, and you ought to be able to explain (and perhaps defend) the connections between formal logic and database technology. And that’s what this book is about. What it does is show, through a series of partly independent, partly interrelated essays, just how various crucial aspects of database technology—some of them very familiar, others maybe less so—are solidly grounded in formal logic. Overall, the goal is to help you realize the importance of logic in everything you do, and also, I hope, to help you see that logic can be fun.

A note from the authors: Dear Reader: "Database is boring." That sentiment is heard all too widely these days. But it's so wrong! The database field is full of important problems still to be solved and interesting issues still to be examined - and some of those problems and issues are explored in this book. Between us, we have nearly 80 years experience in this field, and we're still actively researching, exploring, and learning, as well as helping others do the same. The present book is the latest in a series devoted to these goals; using "The Third Manifesto" (a detailed proposal for the future of database technology) as a foundation, it reports on some of our most recent investigations in this field. Among many other things, it includes the most recent version of "The Third Manifesto" itself; specifications for a conforming language called Tutorial D; and a detailed proposal for a model of type inheritance. Other significant features include: - Extending the foreign key concept - Simplifying queries using image relations - Closer looks at logic and relational algebra - Suggested approaches to "missing information" - Responses to certain "Manifesto" criticisms - Clarifying aspects of normalization The tone of the book overall is naturally somewhat serious, but there are moments of light relief as well. We hope you enjoy it. C.J. Date and Hugh Darwen

Logic and databases are inextricably intertwined. The relational model in particular is essentially just elementary predicate logic, tailored to fit the needs of database management. Now, if you're a database professional, I'm sure this isn't news to you; but you still might not realize just how much everything we do in the database world is - or should be! - affected by predicate logic. Logic is everywhere. So if you're a database professional you really owe it to yourself to understand the basics of formal logic, and you really ought to be able to explain (and perhaps defend) the connections between formal logic and database management. And that's what this book is about. What it does is show, through a series of partly independent and partly interrelate essays, just how various crucial aspects of database technology-some of them very familiar, others maybe less so- are solidly grounded in formal logic. It is divided into five parts: *Basic Logic *Logic and Database Management *Logic and Database Design *Logic and Algebra *Logic and the Third Manifesto There's also a lengthy appendix, containing a collection of frequently asked questions (and some answers) on various aspects of logic and database management. Overall, my goal is to help you realize the importance of logic in everything you do, and also- I hope- to help you see that logic can be fun.