尝试将每行的2个列值相乘。打印所有行的总和

Question

我的目标是计算出股票的总价值。

Table name: Stock
Column names: cost(representing an items cost), s_count(representing quantity).

成本乘以s_count将得出每个项目的总价值。 我将如何将这些列相乘，然后将所有行的结果合计在一起以获得总量？

$selectstock=$db->query("SELECT * FROM stock");
$result = $db->query('SELECT SUM(s_count) AS value_sum FROM stock'); 
$rowes = mysql_fetch_assoc($result); 
$sum = $rowes['value_sum'];
$result2 = $db->query('SELECT SUM(amountfailed) AS value_sum FROM stock'); 
$rowes2 = mysql_fetch_assoc($result2); 
$sum2 = $rowes2['value_sum'];
$uparts = mysql_num_rows($selectstock);
$value = // how do i do this?
print "<h3>Stock overview..</h3><br />
<div><p><br />
Amount of unique parts in stock: {$uparts}<br />
total quantity of stock: {$sum}<br />
Current value of all stock: {$value}<br />
Amount of parts failed: {$sum2}<br />";

如果这是下表...... 例如： -

| id | cost | quantity |
| 1  |  20  |     5    |
| 2  |   5  |    10    |
| 3  |   2  |     2    |
| 4  |  10  |     1    |
| 5  |   7  |     3    |

然后$value需要20 * 5 + 2 * 10..etc

所以$ value将返回185。

Answer 1

这是你想要的吗？

SELECT SUM(s_count*cost) AS value_sum
FROM stock