Nette\Database\Table\Selection::sum PHP Method

    public function sum($column)
    {
        return $this->aggregation("SUM({$column})");
    }

 /**
  * Returns sum of values in a column.
  *
  * @param $column string
  * @return int
  */
 public function sum($column)
 {
     return $this->selection->sum($column);
 }