HSQLDB (HyperSQL DataBase) is the leading SQL relational database engine written in Java. It has a JDBC driver and supports nearly full ANSI-92 SQL (BNF format) plus many SQL:2008 enhancements. It offers a small, fast multithreaded and transactional database engine which offers in-memory and disk-based tables and supports embedded and server modes. Additionally, it includes tools such as a command line SQL tool and GUI query tools.
License: BSD
Written in: JAVA
Operating system: Cross-platform
HeidiSQL is an easy-to-use interface and a "working-horse" for web-developers using the popular MySQL-Database. It allows you to manage and browse your databases and tables from an intuitive Windows® interface.
License: GPL
Written in: Delphi/Pascal
Operating system: Windows
Firebird is an open source relational database management system that runs on Linux, Windows, and a variety of Unix platforms. Firebird offers excellent concurrency, high performance, and powerful language support for stored procedures and triggers.
License: IPL/IDPL
Written in: C++
Operating system: Cross-platform
SQLite is a software library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine. SQLite is the most widely deployed SQL database engine in the world.
License: Public Domain
Written in: C
Operating system: Cross-platform
