MySQL

MYSQL is the most widely used database management system in the world. The database is also used in most TYPO3 installations in conjunction with the Apache web server and the PHP scripting language. We appreciate its reliability and scalability. However, since its acquisition by Oracle in 2010, MYSQL is increasingly criticized in the open source community, to which the TYPO3 Community also belongs, for taking a more and more commercial direction.
It seems, that the final word on that matter is not yet spoken. But the fact that TYPO3 has a database abstraction layer (DBAL) which allows to switch to alternatives is rather reassuring in this situation.

links:

http://www.mysql.com/

https://en.wikipedia.org/wiki/MySQL