MssqlSqlHelper::getSubstrFunction

public function getSubstrFunction($str, $from, $length = null)
{
	$sql = 'SUBSTRING('.$str.', '.$from;

	if (!is_null($length))
		$sql .= ', '.$length;
	else
		$sql .= ', LEN('.$str.') + 1 - '.$from;

	return $sql.')';
}