This book deals almost exclusively with the current, widespread version of SQL, SQL2 (also called SQL/92). Part of the JDBC specification is that SQL2 is its supported SQL version. A newer and not universally supported SQL specification now exists, SQL3 (SQL/99). Among its most fundamental changes is support for abstract data types—an extremely useful change for developers programming in object-oriented languages like Java.
Newer versions of some databases—especially object-relational databases—now support some parts of the SQL3 specification. To take advantage of this important power in newer databases, the new JDBC 2.0 specification has added some extra features. I will note instances when you encounter SQL3-specific functionality, but you should be aware that these SQL calls are bleeding-edge SQL and thus unlikely to be supported by your particular database engine.