Oracle 11g 新特性 -- 只读表（read-only table）说明

一．Read only table说明

在Oracle 11g中，我们可以直接对表的读写权限进行设置：

ALTER TABLE table_name READ ONLY;

ALTER TABLE table_name READ WRITE;

二．示例

--创建表

SQL> create table dave as select * fromdba_objects;

Table created.

--设置为只读：

SQL> alter table dave read only;

Table altered.

--查看表状态：

SQL> select table_name,status,read_onlyfrom dba_tables where table_name='DAVE';

TABLE_NAME STATUS REA

------------------------------ -------- ---

DAVE VALID YES

--这里显示是只读的。

--对Dave表进行DML操作：

SQL> insert into dave select * fromdave;

insert into dave select * from dave

*

ERROR at line 1:

ORA-12081: update operation not allowed ontable "SYS"."DAVE"

SQL> update dave set object_id=88;

update dave set object_id=88

*

ERROR at line 1:

ORA-12081: update operation not allowed ontable "SYS"."DAVE"

SQL> delete from dave;

delete from dave

*

ERROR at line 1:

ORA-12081: update operation not allowed ontable "SYS"."DAVE"

SQL> truncate table dave;

truncate table dave

*

ERROR at line 1:

ORA-12081: update operation not allowed ontable "SYS"."DAVE"

SQL> alter table dave add(namevarchar(20));

alter table dave add(name varchar(20))

*

ERROR at line 1:

ORA-12081: update operation not allowed ontable "SYS"."DAVE"

--虽然表示只读的，但是我们对表进行与索引相关的操作，因为索引修改的是数据字典，和表不相关。

SQL> create index idx_id on dave(object_id);

Index created.

SQL> drop index idx_id;

Index dropped.

--将表改成读写：

SQL> altertable dave read write;

Table altered.

SQL> droptable dave;

Table dropped.