DB_KEY is a unique identifier provided by Interbase.
See the following site (under documentation) for interesting formation
about this feature:
- Claudio Valderrama's resource site: http://www.cvalde.com/

It is present in your situation because you did not explicitly
provide keylinks - to tell IBO how to uniquely identify each record
and either KeyLinksAutoDefine is disabled or the table does not have
a primary key (which is generally not a good idea).

hth

--
Geoff Worboys
Telesis Computing