Datatypes and Collections - Oracle SQL Jumpstart with Examples - page 354

SET (nested table) . Returns a set of the unique values in a
nested table.

SELECT SET(INSTRUMENTS) FROM ARTIST3;

CARDINALITY (nested table) . Returns the number of ele-
ments in a nested table.

SELECT CARDINALITY(INSTRUMENTS) FROM ARTIST3;

POWERMULTISET (nested table) . Returns all set elements
in a collection.
POWERMULTISET_BY_CARDINALITY (nested table,
cardinality) . This function combines the POWERMULTISET and
CARDINALITY functions by returning all set elements with a spec-
ified number of entries for each collection in each row. One could
find every row in a table where that collection has a specified num-
ber of entries.

16.2.6 Metadata Views

This section simply describes metadata views applicable to complex and
object datatypes. Chapter 19 describes the basis and detail of Oracle Data-
base metadata views.

USER_TYPES . Structure of user-defined types.
USER_TYPE_ATTRS . A subset of USER_TYPES except showing
type attributes.
USER_TYPE_METHODS . Once again, a subset of USER_TYPES
except showing methods. A method is a chunk of executable code
attached to and executable by an instance of a type, much like a class
method in an object structure.
USER_NESTED_TABLES and USER_NESTED_TABLE_COLS .
These views describe the structure of nested tables.
USER_VARRAYS . This view describes the structure of VARRAYs.