How can I make a best-sellers list? - php

Question

I want to make a "best sellers" list using information from previous orders. What I currently have is something like this;
Product Quantity
2227 30
1722 3
1851 7
2227 10
1722 4
1863 1
etc....
The first column (product) is the unique ID in the database for each product. The quantity is of course how many items have been sold. Each row is for one order. So the ID 2227 appears two times on this list.
How can I sort this data so that I get a total of how many times ID 2227 is sold?
My PHP at the moment is:
$SQL_best = "SELECT c.company, co.id, cod.productId, cod.quantity
FROM customers c
LEFT JOIN customers_orders co ON c.id = co.custId
LEFT JOIN customers_orders_details cod ON co.id = cod.orderId
WHERE c.reseller =1
AND c.status != 99
AND c.id = ".$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 query
So I need to add together all the $obj_best->productId´s. How do I do that in this case? Or should I be editing my query?

Answer 1

This is an idea, you change the SQL string like this:
$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";