Oracle 11g 新特性--只读表

在oracle 11G之前，无法将单个表设为read only，只能对表空间进行read only操作，11G在这方面做了增强。

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;

下面做一个测试：

建立一个表，将其设置为read only

SQL> conn l5m/l5m
Connected.
SQL> create table test_ro as select * from dba_users;

Table created.

SQL> alter table test_ro read only;

Table altered.

下面做一些dml及ddl操作

SQL> select table_name,status,read_only from dba_tables where table_name='TEST_RO';

TABLE_NAME                     STATUS   REA
------------------------------ -------- ---
TEST_RO                        VALID    YES

SQL> insert into test_ro select * from dba_users;
insert into test_ro select * from dba_users
            *
ERROR at line 1:
ORA-12081: update operation not allowed on table "L5M"."TEST_RO"


SQL> delete from test_ro;
delete from test_ro
            *
ERROR at line 1:
ORA-12081: update operation not allowed on table "L5M"."TEST_RO"


SQL> truncate table test_ro;
truncate table test_ro
               *
ERROR at line 1:
ORA-12081: update operation not allowed on table "L5M"."TEST_RO"


SQL> alter table test_ro add col1 varchar2(100);
alter table test_ro add col1 varchar2(100)
*
ERROR at line 1:
ORA-12081: update operation not allowed on table "L5M"."TEST_RO"

发现dml操作是不允许的，truncatec以及对表结构的更改也不允许。

那哪些操作是允许的？

SQL> create index i_test_ro on test_ro(username);

Index created.

SQL> drop index i_test_ro;

Index dropped.

SQL> drop table test_ro;

Table dropped.

对表增加和删除索引是允许的，甚至可以将read only的表删除也是允许的，因为drop操作是对其数据字典进行操作，和表本身不相关的。所以drop的权限不要随便赋予给普通用户！