一．Read only table说明
在Oracle 11g之前，如果我们想要对一个表设置为只读的，可以通过授予某些用户select 权限。 但是对于表的所有者来说，还是读写的。
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.
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