求助!!怎么把这句话变成用JOIN?

$prefix=C('DB_PREFIX');
$CheckNow = CONTROLLER_NAME.'/'.ACTION_NAME;
$current = M('')->query("SELECT s.id,s.title,s.name,s.tips,s.pid,p.pid as ppid,p.title as ptitle FROM {$prefix}auth_rule s left join {$prefix}auth_rule p on p.id=s.pid where s.name='" .$CheckNow . "'");