The first open source database to feature an SQL interface but sported a flat file back end rather than a true relational file set, actually called Mini SQL but not known as anything but "mSQL" in common usage. Very popular in the 90's as a web back end but gave way to MySQL and SQLite due to licensing issues and is now primarily of historical interest. The original author still supports the product commercially and provides occasional updates, but no one has bothered to port the more recent versions as better alternatives are available, one of the issues being that the author seldom or never folded changes from third party authors into the codebase so that porters constantly had to re-do their work.
- 1998-09-14: mSQL 126.96.36.199 build 4 
- 1999-01-19: mSQL 2.0.6
- 1999-03-17: mSQL 2.0.8
- 1999-04-17: mSQL 2.0.9
- 1999-05-25: mSQL 2.0.10
- 1999-08-24: mSQL 2.0.11
- EMX runtime
- Current version: 4.0 - More operating systems were supported as ports but not by the original author directly, so ports of the most recent versions have dried up but it may be possible to compile the current codebase to other systems without much fuss.
- Commercial - Is open source but released as copyrighted software with a no commercial usage clause.
- Hughes Technologies homepage
- REXX/SQL 2.4 mSQL version
- dbf2msql 2.0 - An utility to convert .dbf files to mSQL tables and back.
- BdBadmin 1.0 - CGI interface to allow mSQL administration via the web.
- Java mSQL JDBC driver
- Hughes Technologies, David Hughes