打印MySQL SUM（）函数的json_encode

Question

I am trying to print with JSON a SUM() of a price.

Currently I am trying:

$query="SELECT SUM(cost) FROM `Service`";
$result = mysql_query($query);

$json = array();
    while($row = mysql_fetch_array($result))
    {
            $json['cost'] = $row['cost'];
    }
    print json_encode($json);
mysql_close();

This returns null.

If I try SELECT cost FROM Service instead, it returns the last cost from the database.

What Im I doing wrong?

Answer 1

supply an ALIAS on the column passed on the aggregate function

SELECT SUM(cost) totalCOST FROM `Service`

so you can fetch the columnName

$json['cost'] = $row['totalCOST'];