如果不为空，请将值插入数据库，并将值设置为'；null'；如果为空 - Insert value to database if not empty and set the value to 'null' if empty

Insert value to database if not empty and set the value to 'null' if empty

我是mysql的新手。所以我的问题是，如果主题字段不为空，我想将数据库中的$状态设置为"正在处理"。如果主题为空，则状态将设置为空。这是我的代码，当我运行它时，状态不会发生任何变化。谢谢

<?php
    if(isset($_POST['submit']))
     {
         $dbhost = 'localhost';
         $dbuser = 'root';
         $dbpass = '';
         $conn = mysql_connect($dbhost, $dbuser, $dbpass);
         mysql_select_db('course');
         if(! $conn )
         {
         die('Could not connect: ' . mysql_error());
         }
         $code= $_POST['code'];
         $subject= $_POST['subject'];
         $status= $_POST['status'];
         $sql = "INSERT INTO form(code,subject,status)
         VALUES('$code','$subject','$status')";
         $retval = mysql_query( $sql, $conn );
         if(!empty($_POST['subject'])) {
                $status = 'IN PROCESS';
            }      
            else $status = 'null';
         if(! $retval )
         {
         die('Could not enter data: ' . mysql_error());
         }
         else
         {
             ?>
             <div class="alert alert-success">
               <strong>Success!</strong> .
             </div>
             <?php
         }

         mysql_close($conn);
      }
 ?>

如果条件，请尝试将Insert语句放在之后。因为CCD_ 2的值已经在条件之前插入。

<?php
        if(isset($_POST['submit']))
         {
             $dbhost = 'localhost';
             $dbuser = 'root';
             $dbpass = '';
             $conn = mysql_connect($dbhost, $dbuser, $dbpass);
             mysql_select_db('course');
             if(! $conn )
             {
             die('Could not connect: ' . mysql_error());
             }
             $code= $_POST['code'];
             $subject= $_POST['subject'];
             $status= $_POST['status'];
             if(!empty($_POST['subject'])) {
                    $status = 'IN PROCESS';
                }      
                else $status = 'null'; 
             //put it here
             $sql = "INSERT INTO form(code,subject,status)
             VALUES('$code','$subject','$status')";
             $retval = mysql_query( $sql, $conn );
             if(! $retval )
             {
             die('Could not enter data: ' . mysql_error());
             }
             else
             {
                 ?>
                 <div class="alert alert-success">
                   <strong>Success!</strong> .
                 </div>
                 <?php
             }

             mysql_close($conn);
          }
     ?>

设置

if(!empty($_POST['subject'])) {
    $status = 'IN PROCESS';
}      
else $status = 'null';

在查询之前

$sql = "INSERT INTO form(code,subject,status)
     VALUES('$code','$subject','$status')";