What is the difference between nested array and associative array?

Question

There are two links http://docs.oracle.com/cd/E11882_01/appdev.112/e25519/composites.htm#LNPLS99981 and

Purpose of using different types of PL/SQL collections in Oracle

by referring above two links i have two doubt

1.Which one is correct nested table?

2.If the oracle doc is correct what is the difference between nested table and associative array?

Answer 1

Here is another difference which is not that commonly known. You can compare two nested tables with = or <> but associative array you cannot.

DECLARE

    TYPE associative_array IS TABLE OF INTEGER INDEX BY PLS_INTEGER;
    a_var_associative_array associative_array;
    b_var_associative_array associative_array;

    TYPE nested_table IS TABLE OF INTEGER;
    a_var_nested_table nested_table := nested_table(1, 2, 3, 4, 5);
    b_var_nested_table nested_table := nested_table(5, 4, 3, 2, 1);

BEGIN

    IF a_var_nested_table = b_var_nested_table THEN
        -- Note, the different order of values!
        DBMS_OUTPUT.PUT_LINE ( 'TRUE' );
    ELSE
        DBMS_OUTPUT.PUT_LINE ( 'FALSE' );
    END IF;

    -- IF a_var_associative_array = b_var_associative_array THEN -> gives you an error! 

END;

When you work with nested tables you can also use Multiset Operators, Multiset Conditions and SET which are not available for associative arrays.