I have developed a database model for an organisation. This organisation has departments that do the same type of work so the schema I designed for one department is the same everywhere. But they are spread in different geographical locations. I have used PostgreSQL v8.2 as the back end and designed the database, while keeping some common details about the departments in a different schema.

The problem is, there are few queries that need to go through more than one department to yield the desired result at head-office. I tried going through the distributed databases theory, but it helped me little. Can anyone please suggest me some practical ways with which I can achieve distributedness?