class method self.add_joins!

# File activerecord/lib/active_record/base.rb, line 1721
        def add_joins!(sql, joins, scope = :auto)
          scope = scope(:find) if :auto == scope
          merged_joins = scope && scope[:joins] && joins ? merge_joins(scope[:joins], joins) : (joins || scope && scope[:joins])
          case merged_joins
          when Symbol, Hash, Array
            if array_of_strings?(merged_joins)
              sql << merged_joins.join(' ') + " "
            else
              join_dependency = ActiveRecord::Associations::ClassMethods::InnerJoinDependency.new(self, merged_joins, nil)
              sql << " #{join_dependency.join_associations.collect { |assoc| assoc.association_join }.join} "
            end
          when String
            sql << " #{merged_joins} "
          end
        end