Say what ?
What would you want to use Lucene and a DB for ? AFAIK (and as far as we use Lucene), Lucene handles searches in text and indexes said text. It is *somewhat* equivalent to stuff you can do with SQL.

Lucene constructs an index from values passed to it representing text, so you could have data in a DB and search a Lucene index, indexed with the same data, but you'd be duplicating information, with all the problems associated with such duplication or doing something that a DB is _usually_ better (and faster) at doing than Lucene (indexing fields and searching through data)...