Moreover, with the increasing use of SQL, many people are learning the language without the benefit (or disadvantage) of knowing the earlier SQL-86, SQL-89, or SQL-92. Neither approach is really adequate for the broad variety of use that typically characterizes SQL programming. Why l Wrote This Book Most of the books on SQL with which I am familiar are oriented toward end users who might type queries into an interactive terminal, or they are critiques of the language. Programmers using almost any modern enterprise- or workgroup-class system will be affected by SQL:1999, whether their applications use Oracle 9i, IBM's DB2, Microsoft's SQL Server, Sybase's Adaptive Server, or any of several other popular database systems. Because of the influence of the relational model of data, few programmers are unaware of relational database systems and many use them daily.
EMS SQL MANAGER SELECT INTO VARIABLE DOES NOT WORK ISO
The fourth version of the ANSI and ISO standard for SQL has now been published, and all programmers concerned with relational database applications will be affected by it. Indeed, like Fortran, C, COBOL, and Java, SQL may be among the most widely used and understood computer languages around. Some years ago, Michael Stonebraker (responsible for relational and object-relational implementations such as Ingres, Postgres, and Illustra) referred to SQL as "intergalactic dataspeak" (a fact that serves as the inspiration for the covers of all of my SQL-related books). SQL is undoubtedly the most widely accepted and implemented interface language for relational database systems. Preface A Word about SQL, Databases, and Programmers Hence, the book will be an indispensable reference both for expert SQL users and for SQL implementers. It also gives a vendor-neutral and very readable view of the SQL language. This book is an excellent guidepost for features that products will likely add in the future. The SQL:1999 standard will influence commercial products for years to come. In the end, you come away understanding the tradeoffs the designers made and have a clear understanding of the final design. He gives one of the more insightful discussions of the concepts and issues that underlie object models. Melton does a wonderful job describing the issues the designers faced and explaining why they chose the path they did. Consequently, designing the SQL object model was a pioneering and extremely delicate task. Object-oriented systems need to address, but they are central to SQL. Jim Melton and Alan Simon, SQL:1999mUnderstanding Relational Language Components (San Francisco: Morgan Kaufmann Publishers, 2002).
SQL must interoperate with almost all languages, it must be persistent, and it has to worry about security and schema evolution. It also hints at the progress in the emerging topics of XML, text, spatial, image, and data mining. 1 This book explains the post-relational SQL:1999 aspects: objects, links, wrappers, and OLAP. Jim wrote a previous volume that explained the "classical" aspects of SQL:1999: the table-row-column stuff. Fortunately, Jim Melton, who is the editor of the SQL:1999 standard (and the SQL-92 standard), is also able to write lucid descriptions that most of us can read. Unfortunately, those standards are written by language lawyers and are very difficult to read.
All these changes are documented in the SQL standards. SQL has also grown to support OLAP (on-line analytic processing) operations and functions, as well as better integration with Java, and to have cleaner support for data links (external files as values) and data wrappers (foreign data sources). SQL's new object model is the basis of the extensions to text, spatial, image and data mining data types and methods. This is an enormous advance in the utility and applicability of the SQL languagemand it goes a long way toward reducing the impedance mismatch between databases and programming languages. The new SQL adds typed-tables, each containing a set of objects accessed via methods. At its core, the old SQL is tables-of-rows-and-columns. This book is a lucid explanation of that evolution. In the last decade, SQL has evolved from the pure-relational model to a postrelational model.
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