An ODBC driver enables an ODBC-compliant application to use a "data source", normally a DBMS. Some non-DBMS drivers exist, for such data sources as CSV files, by implementing a small DBMS inside the driver itself. ODBC drivers exist for most DBMSs, including Oracle, PostgreSQL, MySQL, Microsoft SQL Server (but not for the Compact aka CE edition), Sybase ASE, SAP HANA and DB2. Because different technologies have different capabilities, most ODBC drivers do not implement all functionality defined in the ODBC standard. Some drivers offer extra functionality not defined by the standard.