Database Reference
In-Depth Information
9
Single-Row Functions
In this chapter:
What types of built-in functions are available?
What are single-row functions?
What are the categories of single-row functions?
How do functions work with queries?
What are the options when formatting strings, numbers, and dates?
What are data conversion functions?
How are functions combined?
This chapter uses the queries you have worked with in previous chapters
and expands the way you can use columns by introducing functions. You
will examine the types of functions used for different data types. Finally,
you will experiment with combining functions together for more flexibility.
A function is a built-in PL/SQL program that always returns a single
value. You can use the predefined functions (such as the ones discussed in
this chapter) or you can create your own (see Chapter 24). A function
always returns a single value, as opposed to a procedure, which is a similar
type of program but is able to return more than one value. You can call a
function within a query or other SQL command. You have already seen a
few functions in previous chapters (e.g., NVL and SYSDATE). Before we
examine single-row functions in detail, let's look at Oracle-provided built-
in functions in general. Grouping functions are covered in Chapter 11, reg-
ular expression functions in Chapter 14, object reference functions in
Chapter 16, and XML functions in Chapter 17.
