association_join

# File activerecord/lib/active_record/associations.rb, line 1441
            def association_join
              join = case reflection.macro
                when :has_and_belongs_to_many
                  " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                     table_alias_for(options[:join_table], aliased_join_table_name),
                     aliased_join_table_name,
                     options[:foreign_key] || reflection.active_record.to_s.classify.foreign_key,
                     reflection.active_record.table_name, reflection.active_record.primary_key] +
                  " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                     table_name_and_alias, aliased_table_name, klass.primary_key,
                     aliased_join_table_name, options[:association_foreign_key] || klass.table_name.classify.foreign_key
                     ]
                when :has_many, :has_one
                  case
                    when reflection.macro == :has_many && reflection.options[:through]
                      through_conditions = through_reflection.options[:conditions] ? "AND #{interpolate_sql(sanitize_sql(through_reflection.options[:conditions]))}" : ''
                      if through_reflection.options[:as] # has_many :through against a polymorphic join
                        polymorphic_foreign_key  = through_reflection.options[:as].to_s + '_id'
                        polymorphic_foreign_type = through_reflection.options[:as].to_s + '_type'

                        " LEFT OUTER JOIN %s ON (%s.%s = %s.%s AND %s.%s = %s) "  % [
                          table_alias_for(through_reflection.klass.table_name, aliased_join_table_name),
                          aliased_join_table_name, polymorphic_foreign_key,
                          parent.aliased_table_name, parent.primary_key,
                          aliased_join_table_name, polymorphic_foreign_type, klass.quote(parent.active_record.base_class.name)] +
                        " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [table_name_and_alias,
                          aliased_table_name, primary_key, aliased_join_table_name, options[:foreign_key] || reflection.klass.to_s.classify.foreign_key
                        ]
                      else
                        if source_reflection.macro == :has_many && source_reflection.options[:as]
                          " LEFT OUTER JOIN %s ON %s.%s = %s.%s "  % [
                            table_alias_for(through_reflection.klass.table_name, aliased_join_table_name), aliased_join_table_name,
                            through_reflection.primary_key_name,
                            parent.aliased_table_name, parent.primary_key] +
                          " LEFT OUTER JOIN %s ON %s.%s = %s.%s AND %s.%s = %s " % [
                            table_name_and_alias,
                            aliased_table_name, "#{source_reflection.options[:as]}_id", 
                            aliased_join_table_name, options[:foreign_key] || primary_key,
                            aliased_table_name, "#{source_reflection.options[:as]}_type", 
                            klass.quote(source_reflection.active_record.base_class.name)
                          ]
                        else
                          case source_reflection.macro
                            when :belongs_to
                              first_key  = primary_key
                              second_key = options[:foreign_key] || klass.to_s.classify.foreign_key
                            when :has_many
                              first_key  = through_reflection.klass.to_s.classify.foreign_key
                              second_key = options[:foreign_key] || primary_key
                          end
                          
                          " LEFT OUTER JOIN %s ON %s.%s = %s.%s "  % [
                            table_alias_for(through_reflection.klass.table_name, aliased_join_table_name), aliased_join_table_name,
                            through_reflection.primary_key_name,
                            parent.aliased_table_name, parent.primary_key] +
                          " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                            table_name_and_alias,
                            aliased_table_name, first_key, 
                            aliased_join_table_name, second_key
                          ]
                        end
                      end
                    
                    when reflection.macro == :has_many && reflection.options[:as]
                      " LEFT OUTER JOIN %s ON %s.%s = %s.%s AND %s.%s = %s" % [
                        table_name_and_alias,
                        aliased_table_name, "#{reflection.options[:as]}_id",
                        parent.aliased_table_name, parent.primary_key,
                        aliased_table_name, "#{reflection.options[:as]}_type",
                        klass.quote(parent.active_record.base_class.name)
                      ]
                    when reflection.macro == :has_one && reflection.options[:as]
                      " LEFT OUTER JOIN %s ON %s.%s = %s.%s AND %s.%s = %s " % [
                        table_name_and_alias,
                        aliased_table_name, "#{reflection.options[:as]}_id",
                        parent.aliased_table_name, parent.primary_key,
                        aliased_table_name, "#{reflection.options[:as]}_type",
                        klass.quote(reflection.active_record.base_class.name)
                      ]
                    else
                      foreign_key = options[:foreign_key] || reflection.active_record.name.foreign_key
                      " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                        table_name_and_alias,
                        aliased_table_name, foreign_key,
                        parent.aliased_table_name, parent.primary_key
                      ]
                  end
                when :belongs_to
                  " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                     table_name_and_alias, aliased_table_name, reflection.klass.primary_key,
                     parent.aliased_table_name, options[:foreign_key] || klass.to_s.foreign_key
                    ]
                else
                  ""
              end || ''
              join << %(AND %s.%s = %s ) % [
                aliased_table_name, 
                reflection.active_record.connection.quote_column_name(reflection.active_record.inheritance_column), 
                klass.quote(klass.name)] unless klass.descends_from_active_record?
              join << "AND #{interpolate_sql(sanitize_sql(reflection.options[:conditions]))} " if reflection.options[:conditions]
              join
            end