$sth=$dbh->prepare(qq{select id, quotient from ergebnis order by id});
$sth->execute();
my $array_ref=$sth->fetchall_arrayref();
my %hash;
foreach my $row (@$array_ref) {
   #split the row
   my ($id, $quotient) = @$row;
   $hash{$id} += $quotient;
   print "$id\t$quotient\n";
}