Oracle Advanced PL/SQL Developer Professional Guide

Collection initialization

The persistent collection types—nested tables and varrays—follow features of object orientation. By virtue of their behavior, PL/SQL variables of collection types must be initialized. Initialization is a mandatory activity before the collection is accessed in the PL/SQL program. An uninitialized exception generates the ORA-06531: Reference to uninitialized collection exception.

Associative arrays are the local non-persistent arrays, so no initialization is required for them.

We will discuss some of the ways to initialize a collection type variable in a PL/SQL block:

• Using the default collection constructor during declaration or in the executable section:

  Oracle provides a default constructor (with the same name as the collection ...