Chapter 3. Using Collections

Conceptually, "array" has been a colloquial term in programming glossaries. It refers to a list of similar elements. In Oracle, an array is known by the name, collection. A collection consists of a list of elements of the same type, where each element can be identified by its index or subscript.

A collection works on the same philosophy as an array, a queue, or a linked list works. Collections provide wide scope of usability and applications in database programming. Besides being a performance booster, collections can also be used for data caching mechanisms in programs. It can also be used as database columns, type attributes or subprogram parameters. In this chapter, we shall perform a detailed study on collections, its types and usage in the following topics:

• Collections—an overview

  • Categorization

  • Selection of an appropriate collection type

• Associative arrays

• Nested tables

• Varray

• Collections—a comparative study

• PL/SQL collection methods

• Manipulating collection elements...