What are the difference between assoicate array, nested table and varray ?

Associate array	Nested Table	Varray
Single dimensional	Single dimensional	Single dimensional
Unbounded	Unbounded	Bounded. The row limit has to be specified while declaring
Sparse collection.	Initially Dense collection. Later on can be made sparce by deleting the element in nested table	Dense collections
Can only be used in PL/SQL	Can be used both in PL/SQL as well as a column of a database table.	Can be used both in PL/SQL as well as a column of a database table.
-	Nested table is multiset. I.e. when you store & retrieve elements in Nested table its order is not preserved.	The order is preserved while storing and extracting the elements.