对于这两个子段,Oracle给出了定义:

OBJECT_ID: Object number of the object
DATA_OBJECT_ID: Dictionary object number of the segment that contains the object

也就是说,object_id是schema下唯一的对象的标识,而data_object_id是该对象存储的标识,对于没有独立存储的对象,自然也就没有data_object_id了:

SQL> select object_type,object_id,data_object_id from all_objects where object_type in ('VIEW','PROCEDURE','FUNCTION')
  2  and rownum < 10;

OBJECT_TYPE          OBJECT_ID DATA_OBJECT_ID
------------------- ---------- --------------
VIEW                      1200
VIEW                      1211
PROCEDURE                90952              0
PROCEDURE                90744              0

对于heap table,这两个是相等的:

SQL> select object_name,object_id,data_object_id
  2  from all_objects
  3  where object_name = 'T1';

OBJECT_NAME                     OBJECT_ID DATA_OBJECT_ID
------------------------------ ---------- --------------
T1                                  91066          91066

SQL>

然后建立簇表看看:

SQL> create cluster c1(deptid int);

Cluster created.

SQL> create table test1(deptid int,dname varchar2(35)) cluster c1(deptid);

Table created.

SQL> create table test2(eeid int,deptid int) cluster c1(deptid);

Table created.

SQL> select object_name,object_id,data_object_id
  2  from all_objects
  3  where object_name in('C1','TEST1','TEST2');

OBJECT_NAME                     OBJECT_ID DATA_OBJECT_ID
------------------------------ ---------- --------------
TEST1                               91064          91063
C1                                  91063          91063
TEST2                               91065          91063

可以看到,这时候这三个对象的data_object_id都是C1的;