update_all (ActiveRecord::Base)

    # File lib/active_record/base.rb, line 827
          def update_all(updates, conditions = nil, options = {})
            sql  = "UPDATE #{quoted_table_name} SET #{sanitize_sql_for_assignment(updates)} "

            scope = scope(:find)

            select_sql = ""
            add_conditions!(select_sql, conditions, scope)

            if options.has_key?(:limit) || (scope && scope[:limit])
              # Only take order from scope if limit is also provided by scope, this
              # is useful for updating a has_many association with a limit.
              add_order!(select_sql, options[:order], scope)

              add_limit!(select_sql, options, scope)
              sql.concat(connection.limited_update_conditions(select_sql, quoted_table_name, connection.quote_column_name(primary_key)))
            else
              add_order!(select_sql, options[:order], nil)
              sql.concat(select_sql)
            end

            connection.update(sql, "#{name} Update")
          end