php - 不总结整列

Question

因为它没有计算 first_payment 的 SUM 整列。 我试过“SELECT SUM(first_payment) FROM\Customer Information``，它作为未识别的索引 first_payment 返回。有什么原因吗？

    <?php
    error_reporting(E_ALL);
    ini_set("display_errors", 1);


    $pay=$_REQUEST['payment']; 

    // MySQL database connection, username, password, database name
    $con=mysqli_connect("localhost","user","pass","db_name");

    // Check connection
    if (mysqli_connect_errno()) {
      echo "Failed to connect to MySQL: " . mysqli_connect_error();
    }

    if ($pay=="first") 
      $query="SELECT *, SUM(first_payment) FROM `Customer Information`";
else if ($pay=="second") 
      $query="SELECT *, SUM(second_payment) FROM `Customer Information`";
else if ($pay=="third") 
      $query="SELECT *, SUM(third_payment) FROM `Customer Information`";
else if ($pay=="fourth") 
      $query="SELECT *, SUM(fourth_payment) FROM `Customer Information`";


    $result = mysqli_query($con,$query);

    // Executing and error checking of query
    if (!mysqli_query($con,$query)) {
      die('Error: ' . mysqli_error($con));
    }


    while ($row = mysqli_fetch_array($result)) {
    switch($pay)
    {
       case "first":
          echo $row['first_payment'];
          break;
       case "second":
          echo $row['second_payment'];
          break;
       case "third":
          echo $row['third_payment'];
          break;
       case "fourth":
          echo $row['fourth_payment'];
          break;
       default:
          echo "nothing selected";
    }
    }
    mysqli_close($con);
    ?>

Answer 1

更改您的查询并为您在代码中使用的金额提供正确的别名。试试这个

if ($pay=="first") 
   $query="SELECT *, SUM(first_payment) AS first_payment FROM `Customer Information`";
else if ($pay=="second") 
   $query="SELECT *, SUM(second_payment) AS second_payment FROM `Customer Information`";
else if ($pay=="third") 
   $query="SELECT *, SUM(third_payment) AS third_payment FROM `Customer Information`";
else if ($pay=="fourth") 
   $query="SELECT *, SUM(fourth_payment) AS fourth_payment FROM `Customer Information`";