Question

通过此查询获得的订单总数：

<?php $res = mysqli_query($conn,'SELECT sum(totalprice) FROM orders');
if (FALSE === $res) die("Select sum failed: ".mysqli_error);
$row = mysqli_fetch_row($res);
$sum = $row[0];
echo $sum;?>

通过此查询获得的费用表总计：

<?php $res = mysqli_query($conn,'SELECT sum(amount) FROM expenses');
if (FALSE === $res) die("Select sum failed: ".mysqli_error);
$row = mysqli_fetch_row($res);
$sum = $row[0];
echo $sum;?>

现在我想从订单和费用表中减去总数。示例订单总计-费用总计

Answer 1

如果您提到的sript工作正常，则可以执行以下操作：

$resOrder = mysqli_query($conn,'SELECT sum(totalprice) FROM orders');
if (FALSE === $resOrder) die("Select sum failed: ".mysqli_error);
$row = mysqli_fetch_row($resOrder);
$total = $row[0];
echo $orderTotal;

$resExp = mysqli_query($conn,'SELECT sum(amount) FROM expenses');
if (FALSE === $resExp) die("Select sum failed: ".mysqli_error);
$row = mysqli_fetch_row($resExp);
$expensesTotal = $row[0];
echo $expensesTotal ;

现在要获得结果，就像：

echo $result = $expensesTotal - $orderTotal;

如果遇到任何问题，请告诉我。

Answer 2

您是如此亲密。您只需要为总值赋予不同的变量名即可。

<?php 
    $orderRes = mysqli_query($conn,'SELECT sum(totalprice) as orders_total FROM orders');   //Aliases are a beautiful thing to use. In this case I am giving the sum of orders an alias - orders_total
    $row = mysqli_fetch_assoc($orderRes);
    $ordersTotal = $row['orders_total'];

    $res = mysqli_query($conn,'SELECT sum(amount) as expenses_total FROM expenses');
    $row = mysqli_fetch_assoc($res);
    $expensesTotal = $row['expenses_total']

    $diff = $ordersTotal - $expensesTotal;    //Simply substract expensesTotal from ordersTotal
    echo $diff; ?>

我的表格名称分别为“费用”和“订单”，我想分别获取总计，然后从费用中减去订单总数

2 个答案: