How to create a chart with data from database

my $sth = $dbh->prepare("SELECT a.name,b.name as capital, a.continent,a.region, a.lifeexpectancy,a.surfacearea,a.population FROM country a, city b WHERE a.capital=b.id ORDER BY 1");
$dbh->do("SET search_path to world") or die;
$sth->execute();

my $row=1;
while ($a = $sth->fetchrow_hashref()) {
$worksheet->write($row,0, $a->{name}, $bold);
$worksheet->write($row,1, $a->{capital});
$worksheet->write($row,2, $a->{continent});
$worksheet->write($row,3, $a->{region});
$worksheet->write($row,4, $a->{lifeexpectancy});
$worksheet->write($row,5, $a->{surfacearea});
$worksheet->write($row,6, $a->{population});
$row++;
}

$worksheet = $workbook->add_worksheet("Population Chart");
$worksheet->add_write_handler(qr[\w], \&store_string_widths);
my $chart1 = $workbook->add_chart( type => 'bar', embedded => 1 );

# Configure the series.
$chart1->add_series(
      categories => '=Summary!$A$2:$A$row',
      values     => '=Summary!$G$2:$G$row',
      name       => 'World Population',
      );

# Add another series.
$chart1->add_series(
     categories => '=Summary!$A$2:$A$row',
     values     => '=Summary!$F$2:$F$row',
     name       => 'World Surface Area',
     );

# Add some labels.
$chart1->set_title( name => 'Results of Population analysis' );
$chart1->set_x_axis( name => 'Countries' );
$chart1->set_y_axis( name => 'Population' );

# Insert the chart into the main worksheet.
$worksheet->insert_chart( 'A2', $chart1 );
autofit_columns($worksheet);