I don't have access to a SQL Server Express installation at the moment, but I know that the installer usually installs SQL Server Express with an instance name. What is the default instance name for SQL Server Express installations? I.e., how do you access such an installation by default? Is it localhost\SQLEXPRESS$ ? Is the same name used for both 2005 and 2008 servers?
When installing SQL Express, you'll usually get a named instance called SQLExpress, which as others have said you can connect to with localhost\SQLExpress.
If you're looking to get a 'default' instance, which doesn't have a name, you can do that as well. If you put MSSQLServer as the name when installing, it will create a default instance which you can connect to by just specifying 'localhost'.
Should be .\SQLExpress or localhost\SQLExpress no $ sign at the end
See also here http://www.connectionstrings.com/sql-server-2008
You're right, it's localhost\SQLEXPRESS (just no $) and yes, it's the same for both 2005 and 2008 express versions.
The default instance name after installing is,
Server name:
.\SQLExpress
Authentication:
Windows Authentication
Note: The period in the server Name field means your local machine. For remote machines, use the machine name instead of the period.
This video also helps you to Find your sql server name (instance) for Management Studio .
If you navigate to where you have installed SQLExpress, e.g.
C:\Program Files\Microsoft SQL Server\110\Tools\Binn
You can run SQLLocalDB.exe and get a list of the all instances installed on your machine.
C:\Program Files\Microsoft SQL Server\110\Tools\Binn>SqlLocalDB.exe info
MSSQLLocalDB
ProjectsV12
v11.0
Then you can get further information on the instance.
C:\Program Files\Microsoft SQL Server\110\Tools\Binn>SqlLocalDB.exe info MSSQLLocalDB Name: MSSQLLocalDB
Version: 13.0.1601.5
Shared name:
Owner: Domain\User
Auto-create: Yes
State: Stopped
Last start time: 22/09/2016 10:19:33
Instance pipe name:
in my case the right server name was the name of my computer. for example John-PC, or somth
来源：https://stackoverflow.com/questions/3586196/default-instance-name-of-sql-server-express