There are three types of collections in the Oracle Database 11g family of products. They are the varray, nested table, and associative array datatypes. Collections are powerful structures because they enable you to develop programs that manage large sets of data in memory.
You can build collections of any SQL or PL/SQL datatype. Collections of SQL datatypes work in both SQL and PL/SQL environments but collections of PL/SQL datatypes do not. They only work in PL/SQL.
This chapter explains how to define and work with collections in PL/SQL. There is also some coverage of using collections as database columns. It covers these topics:
Collection set operators