HSQLDB is the leading SQL relational database engine written in Java. It has a JDBC driver and supports a rich subset of ANSI-92 SQL (BNF tree format) plus SQL 99 and 2003 enhancements. It offers a small (less than 100k in one version for applets), fast database engine which offers both in-memory and disk-based tables and supports embedded and server modes. 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.
The product is currently being used as a database and persistence engine in many Open Source Software projects and even in commercial projects and products. In it's current version it is extremely stable and reliable. It is best known for its small size, ability to execute completely in memory, its flexibility and speed.
This feature-packed software is completely free to use and distribute under our licenses , based on the standard BSD license. Completely free of cost or restrictions and fully compatible with all major open source licenses. Java source code and extensive documentation included.
Our group was formed in 2001 and has as its charter the continuation of Thomas Mueller's closed Hypersonic SQL Project. We have actively developed and released six new versions of the database since April 2001. The latest release version features a wide range of new functionality and code rewrite. The project enjoys a top 50 ranking among all SourceForge projects (100,000) with over 380,000 downloads.”