我应该如何编写此代码来使用 sql 数据库中的 php 进行计算

Question

我正在尝试使用一些数据来计算商品的销售额，以使用其 id 来识别每个销售，然后将其显示在屏幕上，从而从 SQL 数据库中获取总数。供进一步使用。

<?php

$dbhost = 'localhost:3306';

                $dbuser = 'root';

                $dbpass = 'mysql';

                $conn = mysql_connect($dbhost, $dbuser, $dbpass);

                if (! $conn ) {

                die('Could not connect: ' . mysql_error());

                }

    $sql = "select item_num * price + tp AS total from buyers where 

 Ref_code = '" . $result16['ref_code'] . "' ";

                mysql_select_db('sales');

  $retval1 = mysql_query($sql, $conn);

  if (!$retval1) { 

die('Could not get data: ' . mysql_error());

}

 $result15 = mysql_fetch_assoc($retval1); 

?>

 <?php echo $result15['total']; ?> '

我希望它在我将 id 传递给 Query 时显示每次销售的总额，但它不显示任何内容。

Answer 1

经过这么多次尝试，我遇到了一个市场购物车，然后我看到了我的错误，即 SQL 变量，我使用 varchar 来存储我的数据，因此查询没有看到 int 或 float 数据，因此它无法计算值并给出想要的结果。在我将我的 SQL 变量更改为 double 然后使用我之前尝试过的公式之后，它起作用了。&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<?php&nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp; &nbsp; &nbsp; $sql1 = "select * from buyers where Ref_code = '" . mysql_insert_id() . "' ";&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; mysql_select_db('sales');&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; $retval1 = mysql_query($sql1, $conn);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (!$retval1) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; die('Could not get data: ' .&nbsp;&nbsp; &nbsp;mysql_error());&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; $result16 = mysql_fetch_assoc($retval1);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ?>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <?php&nbsp;&nbsp; $num1 = $result16['price'];&nbsp; $num2 = $result16['item_num'];&nbsp; $num3 = $result16['tp'];&nbsp; global $num1;&nbsp; global $num2;&nbsp; global $num3;&nbsp; function total()&nbsp;{&nbsp; global $num1;&nbsp; global $num2;&nbsp; global $num3;&nbsp;$sum1 = $num1 * $num2;&nbsp;$sum = $sum1 + $num3;&nbsp;echo "$sum";&nbsp;}&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;?>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <div id ="recipt">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<p>&nbsp; &nbsp;Price: N<?php echo $result16['price'];?> <br><br>&nbsp; <b>Total Amount of Item: <u>N<?php total() ?> </u></b>&nbsp;&nbsp; &nbsp; </p>&nbsp; &nbsp;&nbsp; &nbsp;</div>