The Relational Model for Database Management: Version 2

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Summary: From the creator of relational databases
Review: Dr. Codd, an IBM researcher, first developed the relational data model in 1970 (eg., A relational model of data for large shared data banks: 1970 Communications of the ACM Vol 136:377-387) and spawned a whole industry. In this 1990 book, Codd introduces "Version 2", where he collects a number of his ideas and extends his model. This book is not about specific database package or about SQL (Except for a chapter entitled "Serious Flaws in SQL"), but rather about the concepts behind relational databases. Codd sets the standard and goals that, as yet, no vendor completely delivers. His emphasize on corrective steps for duplicate rows, should not be ignored by vendors.

This is not an easy book to read, with some of his own notation (For example "And clearly S \ U / T = T \ U / S"), but he presents an understanding of the basis of the relational model. The chapter on "Missing information" and his 4 valued logic, with Missing-but-applicable and Inapplicable presents a richer understanding than the usual "Null" concept. His chapter on "View updatability" is helpful for those who has gotten the message "Recordset is not updateable". Fabian Pascal and C.J. Date have reviewed the relational model in articles available online as well as in a Date's recent book "The Database Relational Model: A Retrospective Review and Analysis." Codd challenges the alternatives to the relational model to present a clearly worked out model. With XML going strong, it will be important to develop mathematical underpinnings.