通过创建视图及同义词方式实现普通用户查询X$基表的方法

看到群里有人问普通用户访问基表的问题，测试下如下：

X$基表可以通过创建视图，再对视图创建同义词方式、授权的方式来实现普通用户可以访问基表。

当然了普通用户访基表也是没道理的，理论上没必要，权限控制上也应该是不允许的。此处不考虑合理性，就此问题进行实验。

1.直接对X$基表创建同义词，其它用户无法实现访问。

SQL> show user
USER is "SYS"
SQL> select count(*) from sys.x$kcbwds;

COUNT(*)
----------
8

SQL> CREATE PUBLIC SYNONYM kcbwds FOR sys.x$kcbwds;

Synonym created.

SQL> grant select on sys.x$kcbwds to bys;
grant select on sys.x$kcbwds to bys
*
ERROR at line 1:
ORA-02030: can only select from fixed tables/views
----------
SQL> show user
USER is "BYS"
SQL> select count(*) from sys.x$kcbwds;
select count(*) from sys.x$kcbwds
*
ERROR at line 1:
ORA-00942: table or view does not exist

SQL> select count(*) from kcbwds;
select count(*) from kcbwds
*
ERROR at line 1:
ORA-00942: table or view does not exist

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

2.使用对X$基表创建视图的方法可以实现普通用户访问X$：

SQL> show user
USER is "SYS"
SQL> select count(*) from x$kcbwds;

COUNT(*)
----------
8
SQL> create view testa as select * from sys.x$kcbwds;

View created.

SQL> grant select on sys.testa to bys;

Grant succeeded.

SQL> conn bys/bys
Connected.
SQL> show user
USER is "BYS"
SQL> select count(*) from sys.testa;

COUNT(*)
----------
8
SQL> desc sys.testa
Name                                      Null?    Type
----------------------------------------- -------- ----------------------------
ADDR                                               RAW(4)
INDX                                               NUMBER
INST_ID                                            NUMBER
SET_ID                                             NUMBER
POOL_ID                                            NUMBER
DBWR_NUM                                           NUMBER
BLK_SIZE                                           NUMBER
后面省略。。。

3.可以通过对视图再加同义词方式来实现更简单的访问

SQL> CREATE PUBLIC SYNONYM testb FOR sys.testa;

Synonym created.

SQL> show user
USER is "SYS"
SQL> conn / as sysdba
Connected.
SQL> conn bys/bys
Connected.
SQL> select count(*) from testb;

COUNT(*)
----------
8