HSQLDB, or HyperSQL DataBase, stands out as a premier SQL relational database system developed in Java. It boasts a compact, efficient multithreaded transactional engine that accommodates both in-memory and disk-based tables, functioning effectively in embedded and server configurations. Users can take advantage of a robust command-line SQL interface along with straightforward GUI query tools. HSQLDB is distinguished by its comprehensive support for a vast array of SQL Standard features, including the core language components from SQL:2016 and an impressive collection of optional features from the same standard. It provides full support for Advanced ANSI-92 SQL, with only two notable exceptions. Additionally, HSQLDB includes numerous enhancements beyond the Standard, featuring compatibility modes and functionalities that align with other widely used database systems. Its versatility and extensive feature set make it a highly adaptable choice for developers and organizations alike.