public function _add_having_no_value($column_name, $operator)
{
$conditions = is_array($column_name) ? $column_name : array($column_name);
$result = $this;
foreach ($conditions as $column) {
$column = $this->_quote_identifier($column);
$result = $result->_add_having("{$column} {$operator}");
}
return $result;
}