After you install SQL Server 2012, the Windows authentication is set to mixed-type authentication

How to resolve Sql2012windows Authentication mode to mixed authentication mode ...

Because SQL Server uses Windows only authentication, users cannot connect using SQL Server's logon account, such as SA. Workaround:

1. Select "Use Windows Authentication" to connect to SQL Server;

2. Expand SQL Server Group, right-click the name of the SQL Server server (the Blue section), right-click, and select Properties.

3. Select the "Security" tab and select "SQL Server and Windows Authentication mode".

4. Set the password for the "sa" login, for example, select "SA", right-click, and select "Properties".

5. The SQL Server Login Properties dialog box pops up, as shown in 4. In the "SQL Server Authentication" password bar, enter the latest password. Click the OK button to pop up the Confirm Password dialog box and lose the login password again.

6. Make sure the login is enabled status.

7. Restart the SQL Server service.

Services, management tools, Control Panel, locate the following services, and then restart.

Or, open the SQL Server Configuration tool (All Programs->sql Server 2012-> Configuration Tool->sql Server Configuration Manager), as shown in, select the Blue area, right-click, restart.

Resources:
http://blog.csdn.net/johnson_hejun/article/details/3090028

http://blog.csdn.net/johnson_hejun/article/details/3090076

After you install SQL Server 2012, the Windows authentication is set to mixed-type authentication