code: function (cb) {
              return this.__aggregateDataset().get(sql.COUNT(sql.literal("*")).as("count")).chain(function (res) {
                  return parseInt(res, 10);
              }).classic(cb);
          }
docs: Returns a promise that is resolved with the number of records in the dataset.
  
  @example
  
  // SELECT COUNT(*) AS count FROM table LIMIT 1
  DB.from("table").count().chain(function(count){
  //count === 3;
  });
  
  @param {Function} [cb] the callback to invoke when the action is done.
  
  @return {comb.Promise} a promise that is resolved with the the number of records in the dataset.