Question

I am trying to query top 3 customers. I have 3 tables:

• Customer table (CustomerID, Company)
• Product table (ProductID, ProductName, Price)
• Order table (OrderID, Date, Amount, CustomerID)

OrderID     Date        Amount      CustomerID
19      2012-08-24  20      10043
20      2012-08-24  40      10044
21      2012-08-24  60      10044
22      2012-08-24  80      10042
23      2012-08-24  90      10043
24      2012-08-24  100     10042
25      2012-08-24  50      10041

If you see this table:

• 10042 has ordered $180 worth of products
• 10043 has ordered $110 worth of products
• 10044 has order $100 worth of products

How do I query this information like this:

Top 3 Customers

CustomerID  Company     Cost of Products Ordered
10042       HP      $180
10043       Acer        $110
10044       Sony        $100

Currently I have this mysql but its not displaying as how I want it. Can someone help to point out my mistake?

$query = "SELECT 
    CustomerOrder.CustomerID, CustomerOrder.Amount, 
    Customer.Company, 
    count(CustomerOrder.Amount) as total_amount
FROM 
    `CustomerOrder` 
     INNER JOIN Customer ON Customer.CustomerID = CustomerOrder.CustomerID
GROUP BY CustomerID 
ORDER BY total_amount DESC LIMIT 3";

Currently, i’m getting this:

 Top 3 Customers

CustomerID  Company         Cost of Product Ordered
10042       HP          80.00
10043       Acer            20.00
10044       Sony            40.00

I’m using this code to display:

$result = mysql_query($query);
$num=mysql_numrows($result);
echo "<table border='1'>
<tr>
<th>CustomerID</th>
<th>Company</th>
<th>Cost of Product Ordered</th>

</tr>";

while($row = mysql_fetch_array($result)) 
  {
  echo "<tr>";
  echo "<td>" . $row['CustomerID'] . "</td>";
  echo "<td>" . $row['Company'] . "</td>";
  echo "<td>" . $row['total_amount'] . "</td>";

  echo "</tr>";
  }
echo "</table>";

Answer 1

Use SUM instead of COUNT:

SELECT 
    Customer.CustomerID,
    Customer.Company, 
    SUM(CustomerOrder.Amount) AS total_amount
FROM CustomerOrder
INNER JOIN Customer
ON Customer.CustomerID = CustomerOrder.CustomerID
GROUP BY Customer.CustomerID 
ORDER BY total_amount DESC
LIMIT 3