This pocket reference provides quick-reference information that will help you use Oracle Corporation's extensive set of built-in functions and packages, including those new to Oracle8.
Oracle's PL/SQL language is a programming language providing procedural extensions to the SQL relational database language and to an ever-growing number of Oracle development tools. Among the most useful constructs in the PL/SQL language are the built-in functions and packages.
Built-in functions are constructs that operate on certain types of data (e.g., numeric, character) to return a result. By using functions, you can minimize the coding you need to do in your programs. Functions are described in detail in Steven Feuerstein's Oracle PL/SQL Programming; this comprehensive guide to building applications with PL/SQL has become the bible for PL/SQL developers who have raved about its completeness, readability, and practicality.
Built-in functions fall into several major categories:
- Character functions: Operate on character data. Examples include CONCAT (concatenates two strings into one), LENGTH (returns the length of a string), and REPLACE (replaces a character sequence in a string with a different set of characters).
- Date functions: Operate on dates and supplement the DATE datatype. Examples include SYSDATE (returns the current date and time in the Oracle Server) and LAST_DAY (returns the last day in the month of the specified date).
- Numeric functions: Operate on numeric data. Examples include CEIL (returns the smallest integer greater than or equal to the specified number) and POWER (returns a number raised to a particular power).
- LOB functions: Operate on large object data. Examples include EMPTY_BLOB (returns an empty locator of the binary large object type) and EMPTY_CLOB (returns an empty locator of the character large object type).
- Conversion functions: Perform explicit conversions of different types of data. Examples include TO_CHAR (converts a number or date to a string) and TO_NUMBER (converts a string to a number).
- Miscellaneous functions. Examples include GREATEST (returns the greatest of the specified list of values) and UID (returns the user ID of the current Oracle session).
Built-in packages (collections of PL/SQL objects, such as functions, procedures, and data structures) greatly expand the scope of the PL/SQL language. These packages are described in detail in Feuerstein's and Beresniewicz's book, Oracle Built-in Packages. Built-in packages are built by Oracle Corporation and stored directly in the Oracle database. The functionality of the built-ins is available from any programming environment that can call PL/SQL stored procedures, including Visual Basic, Oracle Developer/2000, Oracle Application Server (for Web-based development), and, of course, the Oracle database itself.
Built-in packages extend the capabilities and power of PL/SQL in many significant ways. For example:
- DBMS_SQL executes dynamically constructed SQL statements and PL/SQL blocks of code.
- DBMS_PIPE communicates between different Oracle sessions through a pipe in the RDBMS shared memory.
- DBMS_JOB submits and manages regularly scheduled jobs for execution inside the database.
- DBMS_LOB accesses and manipulates Oracle8's large objects (LOBs) from within PL/SQL programs.
The book shows how to call all of the commonly used built-in functions and packages. For packages, it also shows the RESTRICT REFERENCES pragmas (needed if you call packages from a SQL statement), as well as the exceptions, constants, and data structures defined in the packages.
John Beresniewicz is currently a product analyst at Savant Corporation (www.savant-corp.com) responsible for design and development of the Q Diagnostic Center for Oracle. Prior to joining Savant, he was an Oracle DBA with eight years experience in large corporate client-server environments. Developing the Q product's server-side PL/SQL engine has given John extensive and unique experience with using Oracle built-in packages to develop large package-based applications. John is also known in the Oracle user community as a frequent speaker on DBA and PL/SQL topics and an active participant in various Oracle online discussion groups. He has given papers at numerous IOUW, ECO, and local Oracle User Groups. At ECO '97, he received the "Outstanding Speaker" award for his talk on using the PL/SQL built-in packages DBMS_PIPE and DBMS_LOCK. John lives with his wife Arlene in Gaithersburg, MD, where they enjoy going to the $2 movie theater. He can be reached by email at jberesni@savant-corp.com.
Chip Dawes has been building and maintaining systems on relational databases since 1988 and with Oracle since 1990. He is currently a consultant with D&D Technologies, a Chicago consultancy. He enjoys working with, lecturing on, and writing about Oracle database administration, client server application development, and Unix system administration. Chip is an Oracle Certified Professional and earned computer science and aerospace engineering degrees from St. Louis University.
Steven Feuerstein is considered one of the world's leading experts on the Oracle PL/SQL language. He is the author or coauthor of Oracle PL/SQL Programming, Oracle PL/SQL Best Practices, Oracle PL/SQL Programming: Guide to Oracle8i Features, Oracle PL/SQL Developer's Workbook, Oracle Built-in Packages, Advanced Oracle PL/SQL Programming with Packages, and several pocket reference books (all from O'Reilly & Associates). Steven is a Senior Technology Advisor with Quest Software, has been developing software since 1980, and worked for Oracle Corporation from 1987 to 1992.
