概述

DB_LINK也是监听网络的一种，是从一个数据库到另一个数据库的一个链接，就是监听网络，配置DB_LINK需要创建相应的权限。

1.私有dblink

配置tns

ora11g =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.16)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = db01)
    )
  )

在test用户下创建私有dblink

22:33:05 TEST@db01> create database link ora11g connect to test identified by "test" using 'ora11g';

Database link created.


22:33:18 TEST@db01> select owner,object_name from dba_objects where object_type='DATABASE LINK';

OWNER                OBJECT_NAME
-------------------- ------------------------------
TEST                 ORA11G

在Test用户下使用dblink查询远程数据库

22:34:13 TEST@db01> select * from test.test01@ora11g;

        ID NAME
---------- --------------------------------------------------
         1 test01
         2 test02
         3 test03


22:34:24 TEST@db01> conn / as sysdba
Connected.

在sys用户下不可以查询，在TEST用户下创建的私有dblink只有该用户拥有权限

22:34:32 SYS@db01> select * from test.test01@ora11g;
select * from test.test01@ora11g
                          *
ERROR at line 1:
ORA-02019: connection description for remote database not found

删除私有dbLink，只有创建私有dblink的用户才可以去删除，其他用户不能删除

23:42:41 SYS@db01> drop database link ORA11G;
drop database link ORA11G
                   *
ERROR at line 1:
ORA-02024: database link not found    ---------sys用户下不行



23:42:57 SYS@db01> conn test/test
Connected.

TEST用户下才可以正常删除
23:43:07 TEST@db01> drop database link ORA11G;

Database link dropped.

2.公有dblink

tns跟前面一样
创建公有dblink

22:32:39 TEST@db01> create public database link ora11g connect to test identified by "test" using 'ora11g';

Database link created.

Elapsed: 00:00:00.01
22:32:46 TEST@db01> 
22:32:53 TEST@db01> select owner,object_name from dba_objects where object_type='DATABASE LINK';

OWNER                OBJECT_NAME
-------------------- ------------------------------
PUBLIC               ORA11G

所有用户下都可以查询远程数据库

23:44:52 SYS@db01>  select * from test.test01@ora11g;

        ID NAME
---------- --------------------------------------------------
         1 test01
         2 test02
         3 test03

Elapsed: 00:00:00.03
23:45:04 SYS@db01> conn test/test    
Connected.
23:45:11 TEST@db01>  select * from test.test01@ora11g;

        ID NAME
---------- --------------------------------------------------
         1 test01
         2 test02
         3 test03

删除公有dblink

22:32:55 TEST@db01> drop public database link ora11g;

Database link dropped.

3.全局dblink，类似公有dblink只是不需要去配置tnsname.ora

create public database link ora11g connect to test identified by "test" using
'(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.51)(PORT = 1521))
) (CONNECT_DATA =
(SERVICE_NAME = db01)
))';