1、T2表结构

SQL> desc t2
Name           Type          Nullable Default Comments 
-------------- ------------- -------- ------- -------- 
OWNER          VARCHAR2(30)  Y                         
OBJECT_NAME    VARCHAR2(128) Y                         
SUBOBJECT_NAME VARCHAR2(30)  Y                         
OBJECT_ID      NUMBER        Y                         
DATA_OBJECT_ID NUMBER        Y                         
OBJECT_TYPE    VARCHAR2(19)  Y                         
CREATED        DATE          Y                         
LAST_DDL_TIME  DATE          Y                         
TIMESTAMP      VARCHAR2(19)  Y                         
STATUS         VARCHAR2(7)   Y                         
TEMPORARY      VARCHAR2(1)   Y                         
GENERATED      VARCHAR2(1)   Y                         
SECONDARY      VARCHAR2(1)   Y   

2、创建中间表

CREATE TABLE T2_1
AS
SELECT * FROM t2 WHERE 1=0;

3、验证T2是否用于重定义（因没有主键，采用rowid实现）

EXEC DBMS_REDEFINITION.CAN_REDEF_TABLE(user, 'T2', DBMS_REDEFINITION.cons_use_rowid);

4、执行表的在线重定义

EXEC DBMS_REDEFINITION.START_REDEF_TABLE(USER, 'T2', 'T2_1','OWNER OWNER, OBJECT_NAME OBJECT_NAME, SUBOBJECT_NAME  SUBOBJECT_NAME, OBJECT_ID OBJECT_ID, DATA_OBJECT_ID DATA_OBJECT_ID, OBJECT_TYPE OBJECT_TYPE, CREATED CREATED, LAST_DDL_TIME LAST_DDL_TIME, TIMESTAMP TIMESTAMP, STATUS STATUS, TEMPORARY TEMPORARY, GENERATED GENERATED, SECONDARY SECONDARY',DBMS_REDEFINITION.cons_use_rowid);

说明：
1）采用单引号列出T2与T2_1表列的对应关系
2）列与列之间采用单引号分割，单引号后面要有空格

5、同步数据（可选）

exec dbms_redefinition.sync_interim_table(user, 'T2', 'T2_1');

6、执行结束在线定义过程

EXEC DBMS_REDEFINITION.FINISH_REDEF_TABLE(user, 'T2', 'T2_1');

7、删除中间表

drop table t2_1 purge;

8、处理T2表（删除隐藏列）

SQL> select col#,name,type# from SYS.COL$ WHERE OBJ#=(select object_id from dba_objects where object_name='T2');
 
      COL# NAME                                TYPE#
---------- ------------------------------ ----------
         1 OWNER                                   1
         2 OBJECT_NAME                             1
         3 SUBOBJECT_NAME                          1
         4 OBJECT_ID                               2
         5 DATA_OBJECT_ID                          2
         6 OBJECT_TYPE                             1
         7 CREATED                                12
         8 LAST_DDL_TIME                          12
         9 TIMESTAMP                               1
        10 STATUS                                  1
        11 TEMPORARY                               1
        12 GENERATED                               1
        13 SECONDARY                               1
         0 SYS_C00014_11081015:39:40$              1
--发现一个多余隐藏列SYS_C00014_11081015:39:40$，我们需要删除
SQL>  alter table t2 set unused ("SYS_C00014_11081015:39:40$");
 
Table altered

SQL>  alter table t2 drop unused columns;
 
Table altered

表在线重定义（有主键）