如何使用带有联接表的mysqli删除查询

我做错了什么？为什么我无法删除结果？下面是我的语法Select语句的作用就像一个符咒，但由于某种原因，当我想删除特定的ID时，它不会起任何作用。只说错误。。你知道我做错了什么吗？如果你能告诉我正确的方向吗？谢谢

require_once 'includes/mysqli_connect.php';
if(isset($_GET['id']) && is_numeric($_GET['id'])) { 
$sql = "SELECT n.entry, FROM `customers` AS c INNER JOIN `notes` as n ON c.user_id = n.user_id WHERE c.user_id={$_GET['id']}";
$result_db = $dbc->query($sql) or die ("Error!");
if ($result_db->num_rows > 0) {
    while($row = $result_db->fetch_assoc()) {
echo    '<form action="select_delete.php" method="post">
' . $row['registration_date'] . '<br/>' . $row['entry'] .'
<input type="hidden" name="id" value="' . $_GET['id'] . '"/>
<input id="click" type="submit" name="submit" value="Delete this Entry" /></form>';
}
} else{
echo 'Information was not retrieved';
}

查询以删除

} elseif(isset($_POST['id']) && is_numeric($_POST['id'])) {
$results = $dbc->query("DELETE `customers`, `notes` FROM `customers` INNER JOIN `notes` ON `notes`.entry = `notes`.entry WHERE `customers`.user_id={$_POST['id']}";
if($results){
echo 'This entry has been deleted!';
} else {
'Error : ('. $mysqli->errno .') '. $mysqli->error;
echo 'NOT DELETED';
}
} else {
echo 'Page accessed in error.. Login if administrator.';
}
$dbc->close();