MariaDB and MySQL are almost same and identical. Since Oracle acquired MySQL in 2008 and may turn it into a commercial product, the original developer and founder of MySQL, Michael Widenius (Monty) released MariaDB based on same MySQL source code under free GNU GPL license.
The MySQL was named after Michael Widenius's daughter My and MariaDB is also named after his younger daughter Maria.
The MariaDB versioning also follows the same pattern as MySQL version number. For Example MariaDB Ver. 5.5 is same as MySQL Ver. 5.5.
The MySQL and MariaDB API's and protocols are compatible and hence all the MySQL ODBC Drivers, OLE DB Providers will work with MariaDB.
MariaDB supports all MySQL database store engines such as MyISAM, BLACKHOLE, CSV, MEMORY, ARCHIVE, and MERGE storage engines but it doesn't support InnoDB. It has introduced XtraDB as a substitute for InnoDB.
Besides the above storage engines it also support the new engines such as
MariaDB speed is faster than MySQL as claimed by it's developer.
SQL language is same in both MariaDB and MySQL so all the queries written in MySQL will work in MariaDB.
MSSQL to MariaDB Converter
MySQL to MariaDB Converter
Oracle to MariaDB Converter