MySQL
MySQL is an open source relational database management system released under GNU General Public License. The Swedish company called MySQL AB develops MySQL.
MySQL is available on many different platforms including Microsoft Windows, the major Linux distributions, UNIX , and Mac OS X.
MySQL is without a doubt the most popular open source database in the world.
MySQL has free and paid versions, depending on its usage (commercial/non-commercial) and features.
"MySQL" is pronounced "my ess-que-ell," in contrast with SQL, pronounced " sequel."
MySQL is offered by most web hosting providers, because of its low cost of ownership and because it can run on many different operating systems.
SQL Tutorial