The server principal is not able to access the database under the current security context in SQL Server MS 2012

Question

I am trying to access my hosting server’s database through SQL Server Management Studio, everything till login is fine but when I use the command use myDatabase

Answer 1

This worked for me:

use 
EXEC  sp_change_users_login @Action='update_one', @UserNamePattern='',@LoginName='';

The problem can be visualized with:

SELECT sid FROM sys.sysusers WHERE name = ''
SELECT sid FROM sys.syslogins WHERE name = '';