如何製作暢銷品清單？

Question

我想使用以前訂單中的信息製作「暢銷品」清單。我現在擁有的是這樣的東西;

Product Quantity 
2227 30 
1722 3 
1851 7 
2227 10 
1722 4 
1863 1 
etc.... 

第一列（產品）是數據庫中每個產品的唯一ID。數量當然有多少項目已經售出。每行是一個訂單。因此ID 2227在此列表中出現兩次。

我該如何對這些數據進行排序，以便共獲得ID 2227的銷售量？

我此刻的PHP是：

$SQL_best = "SELECT c.company, co.id, cod.productId, cod.quantity 
FROM customers c 
LEFT JOIN customers_orders co ON c.id = co.custId 
LEFT JOIN customers_orders_details cod ON co.id = cod.orderId 
WHERE c.reseller =1 
AND c.status != 99 
AND c.id = ".$intCustomerId; 

$result_best = $objDB->sqlExecute($SQL_best); 

*some html code here* 

<table style="margin:0px auto;"> 
<tr> 
    <th>Product</th> 
    <th>Quantity</th> 
</tr> 
<?php 
while($obj_best = $objDB->getObject($result_best)) { 
    if ($obj_best->quantity > 0) { // don't include negatve quantaties (RMA's/refunds) 
    echo "<tr>"; 
     echo "<td>".$obj_best->productId."</td>"; 
     echo "<td>".$obj_best->quantity."</td>"; 
    echo "</tr>"; 
    } 
} 
?> 
</table> 

MySQL查詢

所以我需要加在一起的所有$obj_best->productId的。在這種情況下我該怎麼做？或者我應該編輯我的查詢？

Answer 1

這是一個想法，你改變了SQL字符串是這樣的：

$SQL_best = "SELECT c.company, co.id, cod.productId, 
SUM(cod.quantity) AS quantity 
FROM customers c 
LEFT JOIN customers_orders co ON c.id = co.custId 
LEFT JOIN customers_orders_details cod ON co.id = cod.orderId 
WHERE c.reseller = 1 
AND c.status != 99 
AND c.id = " . $intCustomerId . " 
GROUP BY cod.productId 
HAVING quantity > 0 
ORDER BY quantity DESC";