public function where_in($column_name, $values)
{
if (!$values) {
return $this->_add_where("0", $values);
}
$column_name = $this->_quote_identifier($column_name);
$placeholders = $this->_create_placeholders($values);
return $this->_add_where("{$column_name} IN ({$placeholders})", $values);
}