The previous edition of this book established itself as the most complete and understandable treatment of the SQL standard generally available. Many changes have occurred in the SQL standards world since that edition was published, however: a major new component, the Call-Level Interface (SQL/CLI), was added in 1995. Another major new component, the Persistent Stored Modules feature (SQL/PSM), is nearing completion and is due to be added to the standard in late 1996 or early 1997. The original 1992 standard itself has been significantly changed and corrected through the publication of two extensive Technical Corrigenda, one in 1994 and one in 1996. All of these changes are reflected in this Fourth Edition. Earlier editions of this book established a tradition of careful, clear, and accurate explanation of complex technical material. This new edition continues that tradition.
Several changes have occurred in the SQL standards world since the previous edition of this book was published. First of all, a major new component, the Call-Level Interface (SQL/CLI), was added to the standard in 1995. Second, another major new component, the Persistent Stored Modules feature (SQL/PSM), is currently under development (and indeed nearing completion); SQL/PSM is not yet part of the standard but is virtually certain to become so in the near future. Third, the original standard itself has been significantly changed and corrected through the publication of two Technical Corrigenda, one in 1994 and one in 1996. Taken together, these changes are more than sufficient to justify this new (fourth) edition. At the same time, I have taken the opportunity to extend and improve the text throughout in numerous ways, and in particular to correct a few errors. It is not an exaggeration to say that scarcely a sentence survives intact from the third edition. Acknowledgments
Once again I must thank my coauthor Hugh Darwen for his invaluable contribution (especially in connection with the SQL/PSM and SQL3 appendixes). I would also like to thank Paul Cotton and Frank Pellow for their help with the material on SQL/CLI; Peter Pistor for pointing out an error in the treatment of foreign keys in the previous edition; Mike Sykes for assistance with questions regarding SQL's date and time support (especially in connection with time zones); and Mel Zimowski for assistance with questions regarding SQL's "global transaction" support. I am also indebted to Nelson Mattos, Frank Pellow, and Jeff Richey for their careful reviews of the manuscript.
Finally, I am (as always) deeply indebted to my wife, Lindy, for her support throughout this project; to my editor, Elydia Davis, for her usual sterling job; and to the staff at Addison-Wesley for their usual help and professionalism. Once again it has been a pleasure to work with them. Healdsburg, California
C. J. Date
1996 0201964260P04062001
