Many of you know that I am the main author of O'Reilly's "SQL in a Nutshell". (Here's a shoutout to Brand Hunt and Daniel Kline for their help on the book!) Most of my friends joke that it's a coconut shell, since the book is quite thick, and not the typical walnut shell that many readers expect with the Nutshell series of books.
You find the book at O'Reilly's website at http://www.oreilly.com/catalog/sqlnut2/index.html. You can also find my book at Amazon.com at http://www.amazon.com/gp/product/1565927443/102-0105946-4028970?v=glance&n=283155. Note that Amazon still manages to tick me off by not removing reviews for the 1st edition of my book!
SQL is an excellent example of a standardized programming language designed to meet a specific set of needs. However, SQL is also one of the oldest standards that are still widely used and very popular. So many dialects developed over the years among the various database vendors as they attempted to support a variety of capabilities that were outside of the standard. My book documents all of those variations among vendors, both commercial and open-source, including Oracle, SQL Server, DB2, MySQL, and PostgreSQL.
In the coming weeks, I'll be offering a few excerpts from "SQL in a Nutshell". In the meanwhile, if you'd like a quick primer on the ANSI SQL standard then I'd recommend that you book mark http://troels.arvin.dk/db/rdbms/. The website has a nice little review of many important concepts in SQL and how they differ among the major DBMS vendors.