Prentice Hall Oracle Plsql By Example 3Rd Edition [Electronic resources] نسخه متنی

Chapter 18. Collections

Throughout this book you have explored different types of PL/SQL identifiers or variables that represent individual elements (for example, a variable that represents a grade of a particular student). However, often in your programs you want to have the ability to represent a group of elements (for example, the grades for a class of students). In order to support this technique, PL/SQL provides collection datatypes that work just like arrays available in other third-generation programming languages.

A

collection is a group of elements of the same datatype. Each element is identified by a unique subscript that represents its position in the collection. In this chapter you will learn about two collection datatypes:

table and

varray . In addition, you will learn about multilevel collections that have been introduced in Oracle 9i and are not supported by the previous releases.