php - 当 SELECT SUM() 应该是 xxx 金额时，它总是返回 0

Question

需要有关 SELECT SUM() 的帮助...这是我所有的查询，每当它运行时结果总是 0 任何人看到我的问题似乎都无法弄清楚...

$data = $db->query("SELECT SUM(credit_amount) FROM a_creditpurchase");

$creditsbought = 0;
while($row = $data->fetch(PDO::FETCH_ASSOC)) {
    $creditsbought += $row['credit_amount'];
}
echo $creditsbought;

Answer 1

试试这个

$data = $db->query("SELECT SUM(credit_amount) as sum FROM a_creditpurchase");

$creditsbought = 0;
$row = $data->fetch(PDO::FETCH_ASSOC);
$creditsbought = $row['sum'];

echo $creditsbought;