Standard Security
Server=myServerAddress;Database=myDataBase;User Id=myUsername;Password=myPassword;
Trusted Connection
Server=myServerAddress;Database=myDataBase;Trusted_Connection=True;
Connection to a SQL Server instance
The server/instance name syntax used in the server option is the same for all SQL Server connection strings.
Server=myServerName\myInstanceName;Database=myDataBase;User Id=myUsername;Password=myPassword;
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).
Server=myServerName,myPortNumber;Database=myDataBase;User Id=myUsername;Password=myPassword;
The default SQL Server port is 1433 and there is no need to specify that in the connection string.
Connect via an IP address
Data Source=190.190.200.100,1433;Network Library=DBMSSOCN;Initial Catalog=myDataBase;User ID=myUsername;Password=myPassword;
DBMSSOCN=TCP/IP is how to use TCP/IP instead of Named Pipes. At the end of the Data Source is the port to use. 1433 is the default port for SQL Server. Read more here.
SQL Server 7.0
Enable MARS
Server=myServerAddress;Database=myDataBase;Trusted_Connection=True;MultipleActiveResultSets=true;
Attach a database file on connect to a local SQL Server Express instance
Server=.\SQLExpress;AttachDbFilename=C:\MyFolder\MyDataFile.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.
Attach a database file, located in the data directory, on connect to a local SQL Server Express instance
Server=.\SQLExpress;AttachDbFilename=|DataDirectory|mydbfile.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.
User Instance on local SQL Server Express
The User Instance feature is deprecated with SQL Server 2012, use the SQL Server Express LocalDB feature instead.