DATABASE LINK:

Purpose

Use the CREATE DATABASE LINK statement to create a database link. A database link is a schema object in one database that enables you to access objects on another database. The other database need not be an Oracle Database system. However, to access non-Oracle systems you must use Oracle Heterogeneous Services.

After you have created a database link, you can use it in SQL statements to refer to tables and views on the other database by appending @dblink to the table or view name. You can query a table or view on the other database with the SELECT statement. You can also access remote tables and views using any INSERT, UPDATE, DELETE, or LOCK TABLE statement.

How to create database link

Prerequisites

To create a private database link, you must have the CREATE DATABASE LINK system privilege. To create a public database link, you must have the CREATE PUBLIC DATABASE LINK system privilege. Also, you must have the CREATE SESSION system privilege on the remote Oracle database.

Oracle Net must be installed on both the local and remote Oracle databases.

Connect to TEST database as a Peter user.

SQL> select name, open_mode from v$database;

NAME OPEN_MODE

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

DB11G READ WRITE

SQL> create database link mylink connect to peter identified by peter using 'test';

Database link created.

SQL> select * from emp@mylink;

ID NAME

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

10 Ashwani

20 Rahul

30 Dilip\

30 Richard

SQL> --insert some data in emp table of user PETER in TEST database

SQL> select * from emp@mylink;

ID NAME

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

10 Ashwani

20 Rahul

30 Dilip\

30 Richard

40 Augustin