In CGI::Application::Plugin::Authentication::Driver::DBI the query
generation has no option for extra sql, such as ORDER BY or LIMIT clauses.
In our case, we maintain all passwords for a user, instead of just
updating them. I wanted to do a SELECT with ORDER BY and LIMIT 1 clauses
in order to only get one record for the password table, but there is no
way to supply additional SQL to append to the query.