By default, autocommit is ON, which means that all individual statements are committed as soon as they are executed unless they are in a BEGIN...COMMIT block. If autocommit is OFF, you need to explicitly issue a COMMIT statement to commit a transaction. To disable it, execute:
mysql> SET autocommit=0;
DDL statements, such as CREATE or DROP for databases and CREATE, DROP, or ALTER for tables or stored routines cannot be rolled back.