当我们登录数据库的时候，默认的模式就是当前登陆的用户。但是如果我们以SYSDBA或者SYSOPER的身份登录数据库的时候，确不是这样。以SYSDBA身份登录的默认模式是SYS，以SYSOPER身份登录的默认模式是PUBLIC。

SQL> show user
USER is "SYS"

创建DEMO用户，并且授予CONNECT,RESOURCE权限
SQL> GRANT CONNECT,RESOURCE TO DEMO IDENTIFIED BY DEMO;

Grant succeeded.

授予DEMO用户SYSDBA权限

SQL> GRANT SYSDBA TO DEMO;

Grant succeeded.

以普通用户身份登录数据库

SQL> CONN DEMO/DEMO
Connected.
SQL> SHOW USER
USER is "DEMO"
可以看到当前的模式为DEMO

创建一个表并且插入一条数据

SQL> CREATE TABLE TEST(ID INT,NAME VARCHAR2(10)) TABLESPACE DATA;

Table created.

SQL> INSERT INTO TEST VALUES(1,'YSP');

1 row created.

SQL> COMMIT;

Commit complete.

SQL> SELECT * FROM TEST;

        ID NAME
---------- ----------
         1 YSP

退出SQL*PLUS,然后已SYSDBA的身份登录数据库

SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, Real Application Clusters, OLAP and Data Mining options
[oracle@node2 ~]$ sqlplus "demo/demo as sysdba"

SQL*Plus: Release 10.2.0.1.0 - Production on Mon May 11 20:50:05 2009

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, Real Application Clusters, OLAP and Data Mining options

我们看一下当前的模式是什么。

SQL> SHOW USER
USER is "SYS"
此时我们查询刚刚创建的表将会提示表或者视图不存在的错误。

SQL> SELECT * FROM TEST;
SELECT * FROM TEST
              *
ERROR at line 1:
ORA-00942: table or view does not exist

这时我们在表的前面得加个模式名。

SQL> SELECT * FROM DEMO.TEST;

        ID NAME
---------- ----------
         1 YSP

当我们以SYSOPER的身份登录数据库的时候当前的模式为PUBLIC.

SQL> CONN / AS SYSDBA
Connected.
SQL> SHOW USER
USER is "SYS"
SQL> GRANT SYSOPER TO DEMO;

Grant succeeded.

SQL> CONN DEMO/DEMO AS SYSOPER;
Connected.
SQL> SHOW USER
USER is "PUBLIC"
SQL> CONN DEMO/DEMO
Connected.
SQL> SHOW USER
USER is "DEMO"
SQL>