11g中对象细粒度管理一例

 

11g中oracle提供了细粒度的对象管理。如：视图所依赖的表若发生结构变化，在10g及以前版本中会导致视图失效，而在11g中，若结构变化未影响视图，则视图仍然有效。

在11g中：

SQL> drop table t;

Table dropped

SQL> create table t as select * from emp;

Table created

SQL> create view v_t as select ename,deptno from t;

View created

SQL> select status from dba_objects where object_name='V_T';

STATUS
-------
VALID

SQL> alter table t add a varchar2(2);

Table altered

SQL> select status from dba_objects where object_name='V_T';

STATUS
-------
VALID

 

在10g中：

SQL> drop table t;

Table dropped

SQL> create table t as select * from emp;

Table created

SQL> create view v_t as select ename,deptno from t;

View created

SQL> select status from dba_objects where object_name='V_T';

STATUS
-------
VALID

SQL> alter table t add a varchar2(2);

Table altered

SQL> select status from dba_objects where object_name='V_T';

STATUS
-------
INVALID

 

若视图是select * from table得到的，即使将视图对应的表增加列，视图也不会失效。

SQL> create view v_t2 as select * from t;

View created

SQL> select status from dba_objects where object_name='V_T';

STATUS
-------
VALID

SQL> alter table t add b varchar2(2);

Table altered

SQL> select status from dba_objects where object_name='V_T';

STATUS
-------
VALID

删除一列，视图依然无动于衷：

SQL> alter table t drop column a;

Table altered

SQL> select status from dba_objects where object_name='V_T';

STATUS
-------
VALID

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