Microsoft ODBC Driver 11 for SQL Server
Standard security
Driver={ODBC Driver 11 for SQL Server};Server=myServerAddress;Database=myDataBase;UID=myUsername;PWD=myPassword;
Using SQL Server Express? The server name syntax is ServerName\SQLEXPRESS where you substitute ServerName with the name of the server where SQL Server Express is running.
Trusted Connection
Driver={ODBC Driver 11 for SQL Server};Server=myServerAddress;Database=myDataBase;Trusted_Connection=yes;
Equivalent key-value pair: "Integrated Security=SSPI" equals "Trusted_Connection=yes"
Connecting to an SQL Server instance
The syntax of specifying the server instance in the value of the server key is the same for all connection strings for SQL Server.
Driver={ODBC Driver 11 for SQL Server};Server=serverName\instanceName;Database=myDataBase;Trusted_Connection=yes;
Using a non-standard port
If your SQL Server listens on a non-default port you can specify that using the servername,xxxx syntax (note the comma, it's not a colon).
Driver={ODBC Driver 11 for SQL Server};Server=myServerName,myPortNumber;Database=myDataBase;UID=myUsername;PWD=myPassword;
The default SQL Server port is 1433 and there is no need to specify that in the connection string.
Enable MARS
Driver={ODBC Driver 11 for SQL Server};Server=serverAddress;Database=databaseName;Trusted_Connection=yes;MARS_Connection=yes;
Encrypt data sent over network
Driver={ODBC Driver 11 for SQL Server};Server=serverAddress;Database=databaseName;Trusted_Connection=yes;Encrypt=yes;
Attach a database file on connect to a local SQL Server Express instance
Driver={ODBC Driver 11 for SQL Server};Server=.\SQLExpress;AttachDBFileName=c:\dir\\mydb.mdf;Database=dbName;Trusted_Connection=yes;
Why is the Database parameter needed? If the named database have already been attached, SQL Server does not reattach it. It uses the attached database as the default for the connection.
Database mirroring
If you connect to a database that is being mirrored, your application can take advantage of the drivers ability to automatically redirect connections when a database mirroring failover occurs. You must specify the initial principal server and database in the connection string and the failover partner server.
Driver={ODBC Driver 11 for SQL Server};Server=myServerAddress;Failover_Partner=myMirrorServerAddress;Database=myDataBase;Trusted_Connection=yes;
This one is working only on Windows, not on macOS or Linux. There is ofcourse many other ways to write the connection string using database mirroring, this is just one example pointing out the failover functionality. You can combine this with the other connection strings options available.
Please note if you are using TCP/IP (using the network library parameter) and database mirroring, including port number in the address (formed as servername,portnumber) for both the main server and the failover partner can solve some reported issues.