Php SELECT SUM（）应为xxx金额时始终返回0

需要有关SELECT SUM（）的帮助。。。这是我所有的查询，无论何时运行，结果总是0，任何人都看不到我的问题似乎无法解决

$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;

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;

---

您是否使用

组（信用额）

尝试过SQL查询

---

这很有效基恩谢谢

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

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

---

您的查询没有返回任何名为

credit\u amount

的列，因此没有要添加的内容。另外，对于保证只返回一行的查询，

while

循环似乎有些过分。

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

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