Berkeley DB Reference Guide: Retrieving records

The DB->get method retrieves records from the database. In general, DB->get takes a key and returns the associated data from the database.

There are a few flags that you can set to customize retrieval:

DB_GET_BOTH: Search for a matching key and data item, that is, only return success if both the key and the data items match those stored in the database.
DB_RMW: Read-modify-write: acquire write locks instead of read locks during retrieval. This can enhance performance in threaded applications by reducing the chance of deadlock.
DB_SET_RECNO: If the underlying database is a Btree, and was configured so that it is possible to search it by logical record number, retrieve a specific record.

If the database has been configured to support duplicate records, DB->get will always return the first data item in the duplicate set.