Commercial venues of database software include Oracle, Microsoft, and PostgreSQL. The open source package is MySQL. By learning the free, open source MySQL software, one obtains a foothold on the commercial packages. MySQL has the advantage that it is used by some of the most popular websites on the web. It is built into the content management systems of WordPress, Joomla and Drupal; it is used by the popular phpBB. MySQL operates hand-in-hand with Php.