Recently, we were in need of accessing the remote machine database from the MySQL's trigger. We found the only way to get this done by using the FEDERATED storage engine.
The FEDERATED storage engine is available beginning with MySQL 5.0.3. It is a storage engine that accesses data in tables of remote databases rather than in local tables.
The FEDERATED storage engine is available beginning with MySQL 5.0.3. This storage engine enables data to be accessed from a remote MySQL database on a local server without using replication or cluster technology. When using a FEDERATED table, queries on the local server are automatically executed on the remote (federated) tables. No data is stored on the local tables.