php - 无法将行更新为与当前相同的值吗？

Question

我有一个类似的程序

add_action( 'wp_ajax_case_update', 'case_update' );

function case_update ( )
{
    $id = $_POST['id'];
    $compname = $_POST['compname'];
    $casename = $_POST['casename'];
    $imageurl = $_POST['imageurl'];
    $summary = $_POST['summary'];
    $results = $_POST['results'];

    $thisAction = $_POST['thisAction'];

    $message = "";

    switch ($thisAction)
    {
        case 'add':
        {
            global $wpdb; 
            $message .= $wpdb->query("INSERT INTO cases (compname,casename,imageurl,summary,results) VALUES (" . implode(",", array("'$compname'", "'$casename'", "'$imageurl'", "'$summary'", "'$results'")) . ")")
                       ? 'Successfully added case study ' . $casename . ' to the database.'
                       : 'Error occurred when trying to add case study to database: ' . $wpdb->last_error;
            break;
        }
        case 'delete':
        {
            global $wpdb; 
            $message .= $wpdb->query("DELETE FROM cases WHERE id=" . $id) 
                      ? 'Successfully deleted case study from the database.'
                      : 'Error occurred when trying to delete case study from database: ' . $wpdb->last_error;
            break;
        }
        case 'update':
        {
            global $wpdb;
            $message .= $wpdb->query("UPDATE cases SET compname='$compname',casename='$casename',imageurl='$imageurl',summary='$summary',results='$results' WHERE id=$id")
                      ? 'Successfully updated case study.'
                      : 'Error occurred when trying to update case study in database: ' . $wpdb->last_error;
            break;
        }
        default:
        {
            $message .= 'Didn\'t recognize action.'; 
            break;
        }
    }
    die($message); 
}

我已经在我的 WordPress 主题中构建的许多管理面板中重复使用了这个过程。我在测试过程中刚刚发现，当用户出于某种原因更新到相同值时，case 'update' block 会失败。但由于 $wpdb->last_error; 在发生这种情况时不会打印任何错误，所以我不知道问题到底是什么。

有人解释一下吗？我该如何解决？

Answer 1

将名为 updated 的时间戳列添加到表中，并将 ,updated=now() 添加到 UPDATE 语句中，以便为 update 生成非零值行。