The update script makes a backup of the database, it is in the /root directory.
Plus there is no Admin user anymore so what would be a SQL statement that would get me back in the system?
You can restore it from the backup.
I guess you tried to update a SVN version with a stable version which can not work of course as the SVN version contains more database tables as the stable version. SVN versions can only be updated from svn and not from a stable version!