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

    public function fetchField($column = NULL)
    {
        if ($column) {
            $this->select($column);
        }
        $row = $this->fetch();
        if ($row) {
            return $column ? $row[$column] : array_values($row->toArray())[0];
        }
        return FALSE;
    }

 /**
  * Fetches single field.
  *
  * @param  string|NULL $column
  * @return mixed|FALSE
  */
 public function fetchField($column = NULL)
 {
     return $this->selection->fetchField($column);
 }