Oracle Cross-Database Query Guide

To execute cross-database queries in Oracle, you can achieve this by using a Database Link. Here are the steps to implement it:

1. To establish a database link:
   To create a database link from the target database to the source database, you can use the following SQL statement to create a database link:

CREATE DATABASE LINK link_to_source
CONNECT TO source_user IDENTIFIED BY source_password
USING 'source_database';

link_to_source is the name of the link, source_user and source_password are the username and password of the source database, and source_database is the connection string of the source database.

1. Execute cross-database queries:
   In the target database, you can use the following SQL statement to execute cross-database queries:

SELECT * FROM table_name@link_to_source;

Here, table_name refers to the name of a table in the source database, while link_to_source is the database link created earlier.

By following the steps above, you can execute cross-database queries in Oracle. It is important to ensure that the database link permissions are correctly set and that the network connection is functioning properly.