use DBI;
# do DBI things, like connecting to the database, statement
# preparation and execution

use GD::Graph::Data;
use GD::Graph::bars;

my $data = GD::Graph::Data->new();

while (@row = $sth->fetchrow_array)
{
    $data->add_point(@row);
}

my $chart = GD::Graph::bars->new();
my $gd = $chart->plot($data);