sql-order-by - 結合SQLクエリを「並べ替える」にはどうすればよいですか?

Question

これは機能します...

$sql30 = "SELECT * FROM statuses LEFT JOIN friends ON statuses.userID=friends.lowerFriendID WHERE friends.lowerFriendID != :user_ida
    UNION SELECT * FROM statuses RIGHT JOIN friends ON statuses.userID=friends.higherFriendID WHERE friends.higherFriendID != :user_idb ORDER BY userID DESC";

しかし、ユーザーIDでソートする必要はありません。これは機能しません...

$sql30 = "SELECT * FROM statuses LEFT JOIN friends ON statuses.userID=friends.lowerFriendID WHERE friends.lowerFriendID != :user_ida
    UNION SELECT * FROM statuses RIGHT JOIN friends ON statuses.userID=friends.higherFriendID WHERE friends.higherFriendID != :user_idb ORDER BY id DESC";

これも…

$sql30 = "SELECT * FROM statuses LEFT JOIN friends ON statuses.userID=friends.lowerFriendID WHERE friends.lowerFriendID != :user_ida
    UNION SELECT * FROM statuses RIGHT JOIN friends ON statuses.userID=friends.higherFriendID WHERE friends.higherFriendID != :user_idb ORDER BY `id` DESC";

これも…

$sql30 = "SELECT * FROM statuses LEFT JOIN friends ON statuses.userID=friends.lowerFriendID WHERE friends.lowerFriendID != :user_ida
    UNION SELECT * FROM statuses RIGHT JOIN friends ON statuses.userID=friends.higherFriendID WHERE friends.higherFriendID != :user_idb ORDER BY timestamp DESC";

最新の投稿が最初に表示されるように、「id」または「timestamp」DESC のいずれかで注文する必要があります。あなたの助けに感謝します。ありがとう！