create cluster objs_cluster# ( object_type VARCHAR2(19) ) index ;

create index objs_cluster_idx on cluster objs_cluster#;

create table objs_cluster   -- Ŭ ̺
cluster objs_cluster# ( object_type )
as
select * from all_objects
order by dbms_random.value ;

create table objs_regular   -- Ϲ ̺
as
select * from objs_cluster
order by dbms_random.value;

create index objs_regular_idx on objs_regular(object_type);

alter table objs_regular modify object_name null;  -- ̺ ׼ϵ

alter table objs_cluster modify object_name null;  -- ̺ ׼ϵ 

select /*+ index(t objs_regular_idx) */ count(object_name)
from   objs_regular t
where  object_type = 'TABLE';

select count(object_name)
from   objs_cluster t
where  object_type = 'TABLE';

