Php 不求整列的和

由于这个原因，它没有计算第一笔付款的整列金额<代码>我尝试了“从\客户信息中选择金额（首次付款）”，它作为未识别的索引首次付款返回。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);
    ?>

---

更改查询，并为代码中使用的金额提供正确的别名。请尝试以下操作

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`";

---

请更改查询并为代码中使用的金额总和提供正确的别名。请尝试此操作

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`";

---

除了上面提供的答案，您还必须知道哪里出了问题：

在select语句中，您选择的是字段的总和，而不是试图检索其结果的字段本身，因此出现了错误“未定义索引…”

---

正如上面的答案一样，为总和指定一个别名，并在while循环中使用它来检索它。

除了上面提供的答案之外，您还必须知道出了什么问题：

在select语句中，您选择的是字段的总和，而不是试图检索其结果的字段本身，因此出现了错误“未定义索引…”

如上所述，为总和指定一个别名，并在while循环中使用它来检索它

从查询中提取数组时，请使用MYSQLI_ASSOC：

mysqli\u fetch\u数组（$result，mysqli\u ASSOC）；

或者使用

mysqli\u fetch\u assoc（）

函数：

mysqli\u fetch\u assoc（$result）

对查询中的摘要列使用别名：

例如：

"SELECT *, SUM(first_payment) AS SUMMARY  FROM `Customer Information`";

此外，最好在执行任何操作之前检查

$pay

变量，以避免不必要的数据库连接，如下所示：

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

$pay=$_REQUEST['payment']; 
// first of all: let's check $pay variable:
switch($pay)
{
   case "first":
      $row_index = 'first_payment';
      break;
   case "second":
      $row_index = 'second_payment';
      break;
   case "third":
      $row_index = 'third_payment';
      break;
   case "fourth":
      $row_index = 'fourth_payment';
      break;
   default:
      echo "nothing selected";
      return;  // return if nothing is selected, no need to run any database manipulations.
}

// 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();
}
// prepare query:
$query="SELECT *, SUM(".$row_index.") AS SUMMARY  FROM `Customer Information`";

// Executing and error checking of query
if (!$result = mysqli_query($con,$query)) {
  die('Error: ' . mysqli_error($con));
}
while ($row = mysqli_fetch_array($result,MYSQLI_ASSOC)) {
  echo $row['SUMMARY'];
}
mysqli_free_result($result); // don't forget to free query results
mysqli_close($con);
?>

从查询中提取数组时，请使用MYSQLI_ASSOC：

mysqli\u fetch\u数组（$result，mysqli\u ASSOC）；

或者使用

mysqli\u fetch\u assoc（）

函数：

mysqli\u fetch\u assoc（$result）

对查询中的摘要列使用别名：

例如：

"SELECT *, SUM(first_payment) AS SUMMARY  FROM `Customer Information`";

此外，最好在执行任何操作之前检查

$pay

变量，以避免不必要的数据库连接，如下所示：

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

$pay=$_REQUEST['payment']; 
// first of all: let's check $pay variable:
switch($pay)
{
   case "first":
      $row_index = 'first_payment';
      break;
   case "second":
      $row_index = 'second_payment';
      break;
   case "third":
      $row_index = 'third_payment';
      break;
   case "fourth":
      $row_index = 'fourth_payment';
      break;
   default:
      echo "nothing selected";
      return;  // return if nothing is selected, no need to run any database manipulations.
}

// 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();
}
// prepare query:
$query="SELECT *, SUM(".$row_index.") AS SUMMARY  FROM `Customer Information`";

// Executing and error checking of query
if (!$result = mysqli_query($con,$query)) {
  die('Error: ' . mysqli_error($con));
}
while ($row = mysqli_fetch_array($result,MYSQLI_ASSOC)) {
  echo $row['SUMMARY'];
}
mysqli_free_result($result); // don't forget to free query results
mysqli_close($con);
?>

$query=“SELECT*，SUM（“.$pay.”作为“$pay.”付款。从

客户信息中付款

”$query=“SELECT*，SUM（.$pay.”作为“$pay”。\u从

客户信息中付款

“@Fred-ii-，答案现在看起来好多了。谢谢你的更新！：）非常欢迎。顺便说一句，我真的很喜欢你提出这个解决方案的方式。当我最初看到它时，我做了+1；做得很好,，cheers@Fred-二-，现在答案看起来好多了。谢谢你的更新！：）非常欢迎。顺便说一句，我真的很喜欢你提出这个解决方案的方式。当我最初看到它时，我做了+1；干得好，干杯