public function group($fields, Model $Model = null)
{
if (empty($fields)) {
return null;
}
if (!is_array($fields)) {
$fields = array($fields);
}
if ($Model !== null) {
foreach ($fields as $index => $key) {
if ($Model->isVirtualField($key)) {
$fields[$index] = '(' . $Model->getVirtualField($key) . ')';
}
}
}
$fields = implode(', ', $fields);
return ' GROUP BY ' . $this->_quoteFields($fields);
}