Handle collections

A collection is a group of elements of the same data type, such as a SET, MULTISET, or LIST.

A table might contain a collection stored as the contents of a column or as a field of a ROW type within a column. A collection can be either simple or nested. A simple collection is a SET, MULTISET, or LIST of built-in, opaque, or distinct data types. A nested collection is a collection that contains other collections.