Oracle 11g 新特性：只读表（Read-only）

在Oracle 11g前的版本中，若想对表设置为只读，可以通过赋予SELECT对象权限给这些用户，但表的拥有者还是读写的。而Oracle 11g 允许表标记为只读（read-only)通过ALTER  TABLE 命令。

可以通过下面命令对表读写权限进行设置：

  ALTER  TABLE  table_name READ ONLY;

  ALTER  TABLE  table_name READ WRITE;

简单示例如下：

CREATE  TABLE ro_test (

    id  number

 );

INSERT  INTO  ro_test  VALUES (1);

ALTER  TABLE  ro_test  READ ONLY;

 

任何影响表数据的DML语句和SELECT...FOR UPDATE查询语句都返回ORA-12081错误信息

SQL> INSERT INTO ro_test  VALUES (2);
INSERT INTO ro_test  VALUES (2)
            *
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"

SQL> UPDATE ro_test  SET id = 2;
UPDATE ro_test  SET id = 2
      *
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"

SQL> DELETE FROM ro_test;
DELETE FROM ro_test
            *
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"

影响表数据的DDL语句也受限制

SQL> TRUNCATE TABLE ro_test;
TRUNCATE TABLE ro_test
              *
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"

SQL> ALTER TABLE ro_test ADD (description VARCHAR2(50));
ALTER TABLE ro_test ADD (description VARCHAR2(50))
*
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"

表是只读表但在与之相关的索引上操作不受影响。当表切换回读写模式时DML和DDL操作恢复正常。

SQL> ALTER TABLE ro_test READ WRITE;

Table altered.

SQL> DELETE FROM ro_test;

1 row deleted.

SQL>