Accessing a Nested Collection

If the element of the collection is itself a complex type (collection or row type), the collection is a nested collection. For example, suppose the collection variable, a_set, is a nested collection that is defined as follows: 
EXEC SQL BEGIN DECLARE SECTION;
   client collection set(list(integer not null)) a_set;
   client collection list(integer not null) a_list;
   int an_int;
EXEC SQL END DECLARE SECTION;

To access the elements (or fields) of a nested collection, use a collection or row variable that matches the element type (a_list and an_int in the preceding code fragment) and a Select cursor.