查询将表数据按一列分组并对其他两列的乘积求和

Question

以下代码显示订购产品的单个重量：

$weightsql = 'select op.products_name,
                     op.products_quantity,
                     p.products_weight 
              from ' . TABLE_ORDERS_PRODUCTS . ' op
              left join ' . TABLE_PRODUCTS . ' p on op.products_id = p.products_id
              where op.products_id =  ' . $pro['products_id'];
        
$weightq = tep_db_query( $weightsql );
        
while ($weight = tep_db_fetch_array( $weightq )) {
    if ($category_parent_id != 0) 
      $list_items[] = $weight['products_weight'] . '   ';
}

这显示了订购的每种产品的重量。我所坚持的是，我需要显示总重量，而不是显示单独的重量。例如，如果该产品被订购了 3 次，重量为 7 公斤，则此时的代码显示：

Product  7.00  7.00  7.00

如何让它显示总重量，21公斤？

Answer 1

使用

array_sum()

array_sum() examples
<?php
$a = array(2, 4, 6, 8);
echo "sum(a) = " . array_sum($a) . "\n";

$b = array("a" => 1.2, "b" => 2.3, "c" => 3.4);
echo "sum(b) = " . array_sum($b) . "\n";
?>
The above example will output:
sum(a) = 20
sum(b) = 6.9

Answer 2

只需在循环之前将计数器设置为 0 并在循环期间添加 do it，如下所示：

 $total = 0;
 $weightsql = 'select op.products_name, op.products_quantity , p.products_weight from ' . TABLE_ORDERS_PRODUCTS . ' op left join ' . TABLE_PRODUCTS . ' p on op.products_id = p.products_id where op.products_id =  '.$pro['products_id'];

 $weightq = tep_db_query( $weightsql );

 while ($weight = tep_db_fetch_array( $weightq )){
      if($category_parent_id != 0) {
           $list_items[] = $weight['products_weight'].'   ';
           $total += $weight['products_weight'];
      }

 }

变量 $total 应返回 21。

Answer 3

如果您通过 ID 选择产品，最简单的解决方案是将行数乘以重量。无需将其放入数组中。

Answer 4

$weightsql = 'select op.products_name, sum(op.products_quantity * p.products_weight) as weightsum from ' . TABLE_ORDERS_PRODUCTS . ' op left join ' . TABLE_PRODUCTS . ' p on op.products_id = p.products_id where op.products_id =  '.$pro['products_id'];


echo $weight['weightsum']

感谢您的帮助（！）