php-sql语法，获取带有id变量的随机行w/includes行

对标题措辞不当表示歉意。我正在寻找一个随机的mysql id，其类型值设置为Electro

SELECT * FROM rtsubmissions ORDER BY rand() WHERE `$genretypefix` DESC LIMIT 0, 1

弗雷德解决了第一部分，在WHERE之后ORDER BY。。通过仍然无法使变量工作

编辑：

$sorttype = $_GET['sort'];
$genretype = $_GET['gn'];
$genretypefix = "genre='" . $genretype . "'";
if ($sorttype == 'new') {
    $sql = "
SELECT * FROM rtsubmissions ORDER BY id DESC LIMIT 0, 1
";
} elseif ($sorttype == 'genre') {
$sql = "
SELECT * FROM rtsubmissions WHERE `$genretypefix` ORDER BY rand() DESC LIMIT 0, 1
";
} else {
$sql = "
SELECT * FROM rtsubmissions ORDER BY played DESC LIMIT 0, 1
"; }

EDIT2：根据评论删除，它有效，谢谢