Create and manage SQL databases, control data processing, manage components. Work with in-memory and disk-based tables as well as embedded and server modes of the generated content. Configure execution parameters, access different subsets of info, check integrity, etc.
Download of HSQLDB 2.6.1 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The program is included in Developer Tools. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe. This free Mac app is a product of The HSQL Development Group.
From the developer:
HSQLDB is a relational database engine written in Java, with a JDBC driver, conforming to ANSI SQL:2011. A small, fast, multithreaded engine and server with memory and disk tables, LOBs, transaction isolation, multi-version concurrency, and ACID. It includes a powerful command line SQL tool and simple GUI query tools.
You may want to check out more software for Mac, such as dtsql or Orbada, which might be similar to HSQLDB.