I have installed SQL Server 2008 Express Edition, but by mistake I kept the Windows authentication mode.
Now I want to change that to SQL Server mixed mode. How can I do this?
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sql-server
I had no success with other attempts on a SQL Server 2012. What I did was use SQL Server Management Studio to generate a script to change the value, and got this:
USE [master]
GO
EXEC xp_instance_regwrite N'HKEY_LOCAL_MACHINE', N'Software\Microsoft\MSSQLServer\MSSQLServer', N'LoginMode', REG_DWORD, 2
GO
After that, I enabled the sa account using this:
ALTER LOGIN sa ENABLE ;
GO
ALTER LOGIN sa WITH PASSWORD = '<strongPasswordHere>' ;
GO
...then, I restarted the service, and everything worked!
If the problem is that you don't have access to SQL Server and now you are using mixed mode to enable sa or grant an account admin privileges, then it is far easier just to uninstall SQL Server and reinstall.
Open the registry and search for key LoginMode under:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server
Update the LoginMode value as 2.
From MSDN:
To change security authentication mode:
In SQL Server Management Studio Object Explorer, right-click the server, and then click Properties.
On the Security page, under Server authentication, select the new server authentication mode, and then click OK.
In the SQL Server Management Studio dialog box, click OK to acknowledge the requirement to restart SQL Server.
In Object Explorer, right-click your server, and then click Restart. If SQL Server Agent is running, it must also be restarted.
To enable the SA login:
In Object Explorer, expand Security, expand Logins, right-click SA, and then click Properties.
On the General page, you might have to create and confirm a password for the login.
On the Status page, in the Login section, click Enabled, and then click OK.
One can catch that you may change it through windows registry key
(SQLEXPRESS instance):
"Software\Microsoft\Microsoft SQL Server\SQLEXPRESS\LoginMode" = 2
... and restart service
Source: Stackoverflow.com