Log In to an Instance of SQL Server (Command Prompt)
Applies to: 
SQL Server
This topic describes how to test connectivity to an instance of SQL Server, use the sqlcmd utility.
To log in to the default instance of SQL Server
From a command prompt, enter the following command to connect by using Windows Authentication:
sqlcmd [ /E ] [ /S servername ]
To log in to a named instance of SQL Server
From a command prompt, enter the following command to connect by using Windows Authentication:
sqlcmd [ /E ] /S servername\instancename