protected function _fieldsQuote($alias, $field)
{
list($open, $close) = $this->_quotes;
$aliasing = preg_split("/\\s+as\\s+/i", $field);
if (isset($aliasing[1])) {
list($aliasname, $fieldname) = $this->_splitFieldname($aliasing[0]);
$alias = $aliasname ?: $alias;
return "{$open}{$alias}{$close}.{$open}{$fieldname}{$close} as {$aliasing[1]}";
} elseif ($alias) {
return "{$open}{$alias}{$close}.{$open}{$field}{$close}";
} else {
return "{$open}{$field}{$close}";
}
}