Server Administration :: Materialized Aggregate View Index?

When you create a MAV, you automatically get a hidden column and an index. Here's an example,drop user jon cascade;

grant dba to jon identified by jon;
conn jon/jon
create table emp as select * from scott.emp;
create materialized view mv1 enable query rewrite as
select deptno,sum(sal) from emp group by deptno;
select object_name,object_type from user_objects;
select index_name,column_name from user_ind_columns where table_name='MV1';
select column_name,hidden_column from user_tab_cols where table_name='MV1';
select deptno,"SUM(SAL)",sys_nc00003$ from mv1;