We can now include any tables from these remote sites by qualifying their remote site name in the SQL query.
This example joins three tables:
a local ORDER table in Denver,
a CUSTOMER table in London, and
a ORDERLINE table in Paris.
customer.cust_number = order.customer_number
order.order_number = orderline.order_number;
The local ORDER table will access the CUSTOMER table at London, and the ORDERLINE table in Paris will also be included.
You can also hide the fact that the CUSTOMER and ORDERLINE tables are remote by creating a synonym that hides the database link name:
The SQL could now be written as if the tables were local to the database.
The next lesson takes a look at the transparent network substrate (TNS).
Before moving on to the next lesson, click the Exercise link below to practice defining database links.
Overview Toplogy - Exercise