ecshop首页每个商品下怎么显示已销售量

{
$sql = "select sum(goods_number) from " . $GLOBALS['ecs']->table('order_goods') . " AS g ,".$GLOBALS['ecs']->table('order_info') . " AS o WHERE o.order_id=g.order_id and g.goods_id = " . $goods_id   ;
 return $GLOBALS['db']->getOne($sql);
}

$goods[$idx]['brand_name'] = isset($goods_data['brand'][$row['goods_id']]) ? $goods_data['brand'][$row['goods_id']] : '';

$goods[$idx]['buy_num']= get_buy_sum($row['goods_id']);

{if $goods.buy_num}
{$goods.buy_num}
{else}
0
{/if}