这部分很基础，但是如果搞不清楚，对以后的学习会有影响。
SQL> select * from v$version where rownum=1;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
1.
sqlplus username/password@net_service_name （这是通过网络访问）
C:\Users\Administrator>sqlplus hr/hr@55
SQL*Plus: Release 11.2.0.1.0 Production on 星期日 5月 17 01:14:04 2015
Copyright (c) 1982, 2010, Oracle. All rights reserved.
连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
========================================================
C:\Users\Administrator>sqlplus
SQL*Plus: Release 11.2.0.1.0 Production on 星期日 5月 17 01:16:47 2015
Copyright (c) 1982, 2010, Oracle. All rights reserved.
请输入用户名: hr@55
输入口令:
连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> exit
从 Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
开
================================================================
C:\Users\Administrator>sqlplus /nolog
SQL*Plus: Release 11.2.0.1.0 Production on 星期日 5月 17 01:17:17 2015
Copyright (c) 1982, 2010, Oracle. All rights reserved.
SQL> conn hr/hr@55
已连接。
当然也可以过EZCONNECT连接数据库（easy connect）：
CONNECT username/password@host[:port]/service_name[/instance_name]
CONNECT username/password@[//]host[:port]/service_name
假如你连接没有成功检查一下客户端\network\admin\sqlnet.ora下：
SQL> select * from v$version where rownum=1;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
添加EZCONNECT:
NAMES.DIRECTORY_PATH= (TNSNAMES,EZCONNECT)
下面模拟不添加EZCONNECT:
通过模拟去除服务器端 \network\admin\sqlnet.ora中 NAMES.DIRECTORY_PATH的参数EZCONNECT，客户端任然可以通过EZCO连接，这一点我不是太清楚,希望有朋友可以分享一下。
2.
[oracle@localhost ~]$ sqlplus hr/hr
SQL*Plus: Release 11.2.0.1.0 Production on 星期日 5月 17 02:12:05 2015
Copyright (c) 1982, 2009, Oracle. All rights reserved.
连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
3.
[oracle@localhost ~]$ sqlplus sys/manager as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on 星期日 5月 17 02:12:49 2015
Copyright (c) 1982, 2009, Oracle. All rights reserved.
连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
4.
[oracle@localhost ~]$ sqlplus
SQL*Plus: Release 11.2.0.1.0 Production on 星期日 5月 17 02:13:45 2015
Copyright (c) 1982, 2009, Oracle. All rights reserved.
请输入用户名: hr
输入口令:
连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
5.
[oracle@localhost ~]$ sqlplus /nolog
SQL*Plus: Release 11.2.0.1.0 Production on 星期日 5月 17 02:15:09 2015
Copyright (c) 1982, 2009, Oracle. All rights reserved.
SQL> connect hr/hr
已连接。
SQL> exit
从 Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options 断开
[oracle@localhost ~]$ sqlplus /nolog
SQL*Plus: Release 11.2.0.1.0 Production on 星期日 5月 17 02:15:40 2015
Copyright (c) 1982, 2009, Oracle. All rights reserved.
SQL> connect sys/manager as sysdba
已连接。
此种方法是启动了sqlplus，然后通过connect连接上了数据库.
6.
通过oracle提供的工具或第三方工具：
sql developer ，pl/sql developer,toad,spotlight.......
如果通过网络连接数据库掌握了，这都是非常简单的了。
以上比较简洁的介绍了这些方法，但是并没有罗列全部，比如还有：
HOSTNAME,LDAP,NIS等方法，感兴趣可以自行实验。
