为什么我的数据库插入查询无法在考勤管理系统 php/mysql 中插入记录

Question

我正在学习使用PHP/Mysql的考勤管理系统的教程。由于某些原因，我注意到 INSERT 语句没有被执行，因为如果它执行，$flag变量将设置为 1。

我尝试了一些东西，让我意识到它可能来自 INSERT 语句。我注释掉了 if 语句，以便将$flag设置为 1。当我这样做时，我收到我想要显示的消息"出勤数据已成功插入"，但记录最终不会进入数据库。

.HTML

<div class = "panel panel-default">
  <div class = "panel panel-heading">
  <h2>
  <a class = "btn btn-success" href = "add.php">Add Student</a>
  <a class = "btn btn-info float-right" href = "view_all.php">View All</a>
  </h2>
  <?php if($flag) {?>
  <div class="alert alert-success"> 
  Attendance Data Inserted Successfully
  </div>
  <?php  } ?>
  <?php if($update) {?>
  <div class="alert alert-success"> 
  Student Attendance Updated Successfully 
  </div>
  <?php  } ?>
   <h3><div class="well text-center"> Date:<?php echo date('Y-m-d');?></div></h3>
  <div class= "panel panel-body">
  <form action="index.php" method="post">
     <table class="table table-striped">
     <tr>
     <th>#Serial Number </th><th>Student Name</th><th>Row Number</th><th>Attendance Status </th>
     </tr>
     <?php  $result = mysqli_query($conn, "SELECT * FROM attendance");
       $serialnumber = 0;
       $counter = 0;
       while($row = mysqli_fetch_array($result))
       {
        $serialnumber++;   
     ?>
     <tr>
     <td><?php echo $serialnumber; ?></td>
     <td><?php echo $row['student_name']; ?>
     <input type="hidden" value="<?php echo $row['student_name']; ?>" name="student_name[]">
     </td>
     <td><?php echo $row['row_number']; ?>
     <input type="hidden" value="<?php echo $row['row_number']; ?>" name="row_number[]">
     </td>
     <td>
     <input type="radio" name="attendance_status[<?php echo $counter;?>]" value="Present" 
     <?php if(isset($_POST['attendance_status'][$counter]) && `enter code here`$_POST['attendance_status'][$counter] == "Present"){
        echo "checked = checked";`enter code here`
     }?>
     required>Present    
     <input type="radio" name= "attendance_status[<?php echo $counter;?>]" value="Absent"
     <?php if(isset($_POST['attendance_status'][$counter]) && $_POST['attendance_status'][$counter] == "Absent"){
        echo "checked = checked";
     }?>
     required>Absent 
      </td>
      </tr>
       <?php 
          $counter++;
       }
       ?>
     </table>
<input type="submit" name="submit" value="Submit" class="btn btn-primary">
PHP
<?php
include("db.php");
include("header.php");
$flag = 0;
$update = 0;
if(isset($_POST['submit']))
{
    $date = date('Y-m-d');
    //$date = "2019-03-14";

    $records = mysqli_query($conn, "select * from attendance_records where date = '$date'");  
    $num = mysqli_num_rows($records);
    if($num)
    {
      foreach($_POST['attendance_status'] as $id=>$attendance_status)
      {
        $student_name= $_POST['student_name'][$id];
        $row_number = $_POST['row_number'][$id];

$result = mysqli_query($conn,"update attendance_records set student_name = '$student_name',row_number = '$row_number', attendance_status = '$attendance_status',date = '$date' where date = '$date'");
         if($result){
             $update=1;
         }
      }
    }
    else
    {
        foreach($_POST['attendance_status'] as $id=>$attendance_status)
        {
            $student_name= $_POST['student_name'][$id];
            $row_number = $_POST['row_number'][$id];
            $date = date("Y-m-d H:i:s");

$sql="insert into attendance_records(student_name,row_number,attendance_status,date)values('$student_name','$row_number','$attendance_status','$date')";
    $result = mysqli_query($conn,$sql);
             if($result)
             {
                 $flag = 1;
             }
        }   
    }
}

数据库表出席编号，student_name，row_number

attendance_recordsID，student_name，row_number，attendance_status，日期

我希望在数据库中成功插入记录后，$flag变量应设置为 1，以便显示消息"已成功插入出勤数据"，但这似乎永远不起作用。它不显示消息，当我签入数据库时，没有插入新记录。

Answer 1

执行

查询时

$sql="insert into attendance_records(student_name,row_number,attendance_status,date)values('$student_name','$row_number','$attendance_status','$date')";

attendance_records ID 必须是自动增量的，或者需要在同一查询中插入 ID 值