Part of LAMP. One of the most rowerful SQL servers out there is called MySQL and surprisingly enough, its free. Yes, free. I now use this instead of MS Access, Filemaker or FoxPro (lol). However, since Oracle is now the owner of MySQL there is a fork of MySQL called MariaDB which want to keep the project as open as possible. I am switching to MariaDB because it has more features compared to MySQL which saw little improvements. The commands or Mariadb and MySQL are about the 'same'.
I am also playing with a NoSQL db MongoDB.
br>