Hsqldb
Description
HSQLDB is a relational database management system written in Java. It is based on Thomas Mueller's discontinued Hypersonic SQL Project. He later developed H2 as a complete rewrite.
HSQLDB is available under a BSD license.
It has a JDBC driver and supports a rich subset of SQL-92, SQL-99, and SQL:2003 standards. It offers a fast, small (less than 100k in one version, around 600k in the standard version) database engine which offers both in-memory and disk-based tables. Embedded and server modes are available.
Additionally, it includes tools such as a minimal web server, in-memory query and management tools (can be run as applets), and a number of demonstration examples. HSQLDB is currently being used as a database and persistence engine in many open source software projects, such as OpenOffice.org Base and the Standalone Roller Demo, as well as in commercial projects and products, such as InstallShield or InstallAnywhere (starting with version 8.0).
It is best known for being bundled with Hibernate, a popular object-relational mapping library for Java. It can also run on free Java runtimes such as Kaffe.