my $dbh = DBI->connect( ... );

my $sth1 = $dbh->prepare(
    'SELECT studentid, ranker1, ranker2 FROM students'
);
$sth1->execute();

my %ranked;
while ( my $row = $sth1->fetchrow_arrayref() ) {
    my $calc_rank = $row->{ranker1} + $row->{ranker2};

    %ranked{ $row->{studentid} } = $calc_rank;
}

my @rank_order = sort {
    $ranked{$a} <=> $ranked{$b}
} keys( %ranked );


my $sth2 = $dbh->prepare(
    'SELECT * FROM students WHERE studentid=?'
);

for my $studentid ( @rank_order ) {
    $sth2->execute( $studentid );

    my $row = $sth2->fetchrow_hashref();
    while ( my($k, $v) = each( %$row ) ) {
        print( "$k: $v\n" );
    }

    print( "\n\n" );
}