update

# File activerecord/lib/active_record/base.rb, line 2479
      def update(attribute_names = @attributes.keys)
        quoted_attributes = attributes_with_quotes(false, false, attribute_names)
        return 0 if quoted_attributes.empty?
        connection.update(
          "UPDATE #{self.class.quoted_table_name} " +
          "SET #{quoted_comma_pair_list(connection, quoted_attributes)} " +
          "WHERE #{connection.quote_column_name(self.class.primary_key)} = #{quote_value(id)}",
          "#{self.class.name} Update"
        )
      end