Preface

Millions of application developers and database administrators (DBAs) around the world use software provided by Oracle Corporation to build complex systems that manage vast quantities of data. At the heart of much of Oracle's software is PL/SQLa programming language that provides procedural extensions to Oracle's version of Structured Query Language (SQL) and serves as the programming language within the Oracle Developer toolset.

PL/SQL figures prominently as an enabling technology in almost every new product released by Oracle Corporation. Software professionals use PL/SQL to perform many kinds of programming functions, including:

• Implementing crucial business rules in the Oracle Server with PL/SQL-based stored procedures and database triggers

• Generating and managing XML documents entirely within the database

• Linking web pages to an Oracle database

• Implementing and automating database administration tasksfrom establishing row-level security to managing rollback segments within PL/SQL programs

PL/SQL was modeled after Ada,^[*] a programming language designed for the United States Department of Defense. Ada is a high-level language that emphasizes data abstraction, information hiding, and other key elements of modern design strategies. As a result of this very smart design decision by Oracle, PL/SQL is a powerful language that incorporates many of the most advanced elements of procedural languages, including:

^[*] The language was named "Ada" in honor of Ada Lovelace, a mathematician who is regarded by many to have been the world's first computer programmer. For more information about Ada, visit http://www.adahome.com.

• A full range of datatypes from number to string, and including complex data structures such as records (which are similar to rows in a relational table), collections (which are Oracle's version of arrays), and XMLType (for managing XML documents in Oracle and through PL/SQL)

• An explicit and highly readable block structure that makes it easy to enhance and maintain PL/SQL applications

• Conditional, iterative, and sequential control statements, including a CASE statement and three different kinds of loops

• Exception handlers for use in event-based error handling

• Named, reusable code elements such as functions, procedures, triggers, object types (akin to object-oriented classes), and packages (collections of related programs and variables)

PL/SQL is integrated tightly into Oracle's SQL language: you can execute SQL statements directly from your procedural program without having to rely on any kind of intermediate Application Programming Interface (API) like Java DataBase Connectivity (JDBC) or Open DataBase Connectivity (ODBC). Conversely, you can also call your own PL/SQL functions from within a SQL statement.

While the majority of PL/SQL users are programmers, it is also a language used by many database administrators. A solid working knowledge of PL/SQL is, in fact, crucial for Oracle DBAs.