更新数据库，不再在列表中添加相同的用户名

Question

    $update_list = "";
foreach($keys as $k)
{
    if(!isset($_GET[$k]) || empty($_GET[$k]))
    {
        exit("error");
    }

    $update_list .= ($k != "username") ? "{$k}={$_GET[$k]},":"";
}
$update_list = substr($update_list, 0, -1);

$con = new PDO("mysql:host=localhost;port=3306;dbname=highscores", "root", "");
$row_list = implode(",", $keys);
$question_marks = substr(str_repeat("?,", sizeof($keys)), 0, -1);

$query = "INSERT INTO `highscores` ({$row_list}) VALUES ({$question_marks}) ON DUPLICATE KEY UPDATE {$update_list}";

When i logout it will add an another username with same name into the list. What i wan't is that when a user logs out it will update the stats and not create a same username with the updated stats into the list. What is wrong here.

mvg.

Answer 1

The SQL query should not be INSERT INTO but UPDATE try writing something like:

$query = "UPDATE `highscores`SET({$question_marks}) WHERE username=usernameToUpdate";

replace the 'usernameToUpdate' to the username related to the 'highscore' you want to change. It's probably better to use 'userId' instead of username but it can done either way,

Answer 2

My guess is you haven't actually set up a primary key in the database. ON DUPLICATE KEY will only trigger if you have a unique key defined. All primary keys are unique.

Every table should have a primary key. While it's technically not required, if you want your queries to not have awful performance, then you need to have a primary key.

If I am wrong and you do have a primary key set up, try setting up a unique index on username. That should fix your problem.