Firebird is an SQL RDBMS with rich support for ANSI SQL (e.g., INSERT...RETURNING
) including UDFs and PSQL stored procedures, cursors, and triggers. Transactions provide full ACID-compliant referential integrity.
The database requires very little manual maintenance once set up, making it ideal for small business or embedded use.
When installed as a traditional local or remote (network) database server, Firebird can grow to terabyte scale with proper tuning---although PostgreSQL may be a better choice for such very large environments.
Firebird can also be embedded into stand-alone applications that don't want or need a full client & server. Used in this manner, it offers richer SQL support than SQLite as well as the option to seamlessly migrate to a client/server database later.