Chapter 3. Oracle Database Functions

Every DBA needs to know about built-in functions. Many of the day-today tasks of a DBA involve queries, and these queries often need to transform or summarize information in database tables and views. Many DBAs will also create and maintain a library of customized functions (also known as user-defined functions) for business areas in the company and help to deploy these user-defined functions.

This chapter covers the built-in functions and provides an introduction to user-defined functions. However, before we dig into the functions themselves, we'll talk about some of the general rules for building queries, including how the DUAL table is used, how NULL values work, and how numbers and strings are constructed.