HSQLDB is described as '(Hyper Structured Query Language Database) is a relational database management system written in Java. It has a JDBC driver and supports a large subset of SQL-92 and SQL:2008 standards. It offers a fast, small (around 1300 kilobytes in version 2' and is a relational database in the development category. There are more than 50 alternatives to HSQLDB for a variety of platforms, including Windows, Linux, Mac, Web-based and Self-Hosted apps. The best HSQLDB alternative is DBeaver, which is both free and Open Source. Other great apps like HSQLDB are SQLite, PostgreSQL, MySQL Community Edition and MariaDB.