If you want to use a connection string for connecting to a database, or if your application requires it, you must specify either a DSN (data source name), a File DSN, or a DSN-less connection in the string. The difference is whether you use the DSN=, FILEDSN=, or the DRIVER= keyword in the connection string, as described in the ODBC specification. A DSN or FILEDSN connection string tells the driver where to find the default connection information. Optionally, you may specify attribute=value pairs in the connection string to override the default values stored in the data source.

The DSN connection string has the form:

The FILEDSN connection string has the form:

The DSN-less connection string specifies a driver instead of a data source. All connection information must be entered in the connection string because the information is not stored in a data source.

The DSN-less connection string has the form:

Connection Option Descriptions and Configure Location Dialog Box Descriptions give the names and descriptions of the attributes, as well as the initial default value when the driver is first installed.

An example of a DSN connection string with overriding attribute values for XML is:

A FILEDSN connection string is similar except for the initial keyword:

A DSN-less connection string must provide all necessary connection information: