sql-order-by - 如何“排序”加入 sql 查询？

Question

这有效...

$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";

但我不需要按用户 ID 排序，这不起作用......

$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";

这也不...

$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";

这也不...

$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";

我需要按“id”或“timestamp”DESC 排序，以便最先显示最新的帖子。非常感谢您的帮助。谢谢你！