add_joins!

# File activerecord/lib/active_record/base.rb, line 1440
        def add_joins!(sql, options, scope = :auto)
          scope = scope(:find) if :auto == scope
          join = (scope && scope[:joins]) || options[:joins]
          case join
          when Symbol, Hash, Array
            join_dependency = ActiveRecord::Associations::ClassMethods::InnerJoinDependency.new(self, join, nil)
            sql << " #{join_dependency.join_associations.collect { |assoc| assoc.association_join }.join} "
          else
            sql << " #{join} "
          end
        end