PHP Code:
$e = mysql_query("SELECT * FROM tabela t1 WHERE id_korisnik=6
AND EXISTS(SELECT * FROM tabela t2
WHERE t2.ponuda>=t1.ponuda
GROUP BY id_predmet
HAVING COUNT(id_predmet) = 1)
GROUP BY id_predmet");
while($row = mysql_fetch_array($e)){
echo $row[0], ' | ', $row[1], ' | ', $row[2], ' | ', $row[3], '<br />';
};