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Rating: 
Summary: Comments and Features
Review: "I highly recommend this book to anyone interested in temporal data---either designing and building databases that record information over time, or just understanding the concepts that underlie representing temporal information... an excellent job of organizing and summarizing this important area." -- From the foreword by Jim Gray, Microsoft Research"...a long time in the making, not only because the subject matter can seem overwhelmingly complex if not presented carefully, but also because of the great number of examples that Snodgrass has taken from real application systems and translated into standard SQL." -- From the foreword by Jim Melton, Oracle Corporation FEATURES * Offers advice on recording temporal data using SQL data types, defining appropriate integrity constraints, updating temporal tables, and querying temporal tables with interactive and embedded SQL. * Provides case studies detailing real-world problems and solutions in areas such as event data, state-based data, partitioned data, and audit logs. * Contains over 400 code fragments with detailed explanations. * Includes a CD-ROM containing the code fragments implemented for IBM DB2 Universal Database (UDB), Ingres, Informix-Universal Server, Microsoft Access, Microsoft SQL Server, Sybase SQLServer, Oracle8 Server, and UniSQL, as well as evaluation copies of the programs discussed in the book.
Rating: 
Summary: Timely ! Overall, this is the best available.
Review: I have spent quite a bit of time working on databases that involve time issues. I've looked at much of the published material available, including Date's recent book, dozens of articles, conference proceedings, etc. Overall this is the best available. After I absorbed a lot of this book, I felt there could have been a more concise version of the concepts. Maybe someone will come out with a concise, well illustrated 100 pp. tutorial that is dramatically better, but it hasn't happened yet. Even though there are a lot of code samples, there is still a BIG leap to get to a production system. It is too bad that something like SQL/Temporal won't be coming out as a standard anytime soon. However, with conventional SQL you can still go a long way in developing databases just by using the Bitemporal design principles. Overall, if you work with time history, etc. in databases, you can't afford to not be studying this book.
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Summary: Timely ! Overall, this is the best available.
Review: I've used this book while working as the lead data architect on several large database projects, and it's been a lifesaver. It brings rigor and discipline to a very difficult area for SQL (true relational) databases: handling, reporting on, and storing the changing [versions of] data over time. The concepts are themselves quite difficult and challenging, and I would be loathe to even attempt to build a system tracking changing data over time without this book's priceless assistance. Another reviewer, an instructor, didn't like the book: it is not a tutorial and may be hard to use, understand, or follow if you are not already working on a problem that this book can help you solve. But if you are involved in creating (say) an insurance application that must handle retroactivity, or a financial system that must be able to re-create an earlier financial report and explain why today's version of Q2 is different from yesterday's, then you NEED this book.
Rating: 
Summary: Widely and immediately useful
Review: I've used this book while working as the lead data architect on several large database projects, and it's been a lifesaver. It brings rigor and discipline to a very difficult area for SQL (true relational) databases: handling, reporting on, and storing the changing [versions of] data over time. The concepts are themselves quite difficult and challenging, and I would be loathe to even attempt to build a system tracking changing data over time without this book's priceless assistance. Another reviewer, an instructor, didn't like the book: it is not a tutorial and may be hard to use, understand, or follow if you are not already working on a problem that this book can help you solve. But if you are involved in creating (say) an insurance application that must handle retroactivity, or a financial system that must be able to re-create an earlier financial report and explain why today's version of Q2 is different from yesterday's, then you NEED this book.
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Summary: Theoretical,takes work to translate it into something useful
Review: One can tell that this work stems from the research of the author but he fails to translate it into something useful. It took a lot of effort to translate the concepts into something that my students would use in the database real world. I got sick of the little sidebars that had interesting but useless tidbits concerning notions of time. This is not for the developer but it might be useful for someone that is SQL knowledgeable that wants to check out some variations on time and temporal specifications.
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Summary: Quickly understand temporal data
Review: Professor Snodgrass has effectively communicated temporal data to me with this top-notch book. I have been designing systems for 25+ years and, for me, this book ranks with Donald Knuth's, "Art of Programming: Fundamental Algorithms (first edition)" and Charles Petzold's "Programming Windows", for its impact, in particular on my thinking process in software development. Every system I review, every table I design, every object that I design be considered differently than before I read this book. His analogies are "country", but important. It took three settings of an hour each on 10 pages until the concepts really sank in. I have seen these constructs in Data Warehouses, but now I see a future for these in transactional systems. Every time based system will eventually incorporate these concepts (and new SQL tools) - In particular all accounting systems including banking, brokerage (especially portfolio management), tax accounting. For example, right now we are working on a system to track and manage vendor problems in a "just in time" manufacturing environment. If our tables had been designed with these temporal concepts, we would be able to more effectively communicate trends to our management users. Those people who are familiar with these concepts may find it boring, but for those of us learning, I say thank you!
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Summary: Database designer will learn to think of NOW in PAST terms
Review: The one-of-a-kind book is a practical research on how the real world changes over time effect the viability of database design.
The author provides many solutions to real-life problems and (most important!) 'gotchas' of the these solutions. The examples are provided for many popular DBMSs(from MS Access to Oracle).
The reader benefits greatly from the superb organization of material, clear language and good illustrations.
The sidebar notes on history of time-measuring devices provide a nice break from the 'heavy-duty' stuff.
I bought my copy two month ago and it has already became a one of the best-thumbed books on my professional shelf.
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Summary: Consise best-practices for date-time handling.
Review: This is a book EVERY programmer that deals with databases should read. It explains the evils of NULL date/datetimes and how to properly optimize a database design for real-world queries. Follows several applications through the evolution of time-senstive queries, clearly distinguishing the concepts of "current time", "effective time" and "transaction time", which trip up developers over and over.
Rating:
Summary: Consise best-practices for date-time handling.
Review: This is a book EVERY programmer that deals with databases should read. It explains the evils of NULL date/datetimes and how to properly optimize a database design for real-world queries. Follows several applications through the evolution of time-senstive queries, clearly distinguishing the concepts of "current time", "effective time" and "transaction time", which trip up developers over and over.
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