my $statement = "SELECT name, number, nw, land, strat, last_updated, ownerID 
                        FROM someTable                  ORDER BY number ASC";
        $sth = $dbh->prepare($statement);                              
        $sth->execute() or die "Can't execute the query: $sth->errstr";
        my $ref = $sth->fetchall_hashref('number');
        for my $key( %$ref ) {                                  
            $ref->{$key}->{nw} = addComma( $ref->{$key}->{nw} );
        }                            
        my $countries = $sth->rows();
        $sth->finish;

##</code><code>##

my $rows = $dbh->selectall_arrayref(".....");

##</code><code>##

my $ref = $sth->fetchall_hashref('number');