$sqla = mysql_query("SELECT * FROM eventos ORDER BY cod DESC LIMIT 0,1") or die("ERRO NO SQL A");
$rowa = mysql_num_rows($sqla);
while($rowa = mysql_fetch_assoc($sqla)){
$cod_evento = $rowa['cod'];
};
$sqlb = mysql_query("SELECT * FROM fotos WHERE `cod_evento`='$cod_evento' ORDER BY cod") or die("ERRO NO SQL B");
$rowb = mysql_num_rows($sqlb);
while($rowb = mysql_fetch_assoc($sqlb)){
?>

};
?>