Php 比较不同表中的2列Mysql并删除

好的，我的问题是

我有一个支持自动登录的拍卖网站，但是当拍卖被自动登录时，它不会清除旧的条目，所以我打算编写一些php代码，并将其作为cronjob运行，以清除条目，比如2天左右，引用的表是probid_auctions&probid_auction_media，列是auction_id，我想在probid_auction_media中获取列auction_id，并将其与probid_auction中的列auction_id进行比较，删除probid_auction_media中不匹配的任何条目

现在测试这个

mysql_connect($host, $username, $password);
mysql_select_db("b1396hos_database1") or die( "Unable to select database");
$db->query("DELETE * FROM  probid_auction_media 
WHERE auction_id NOT IN (SELECT DISTINCT auction_id FROM probid_auctions");

使用这样的查询

DELETE
FROM probid_auction_media
WHERE auction_id NOT IN(SELECT
                      probid_auction_media.auction_id
                    FROM probid_auctions,
                      probid_auction_media
                    where probid_auctions.auction_id != probid_auction_media.auction_id);

---

您应该向我们展示您所做的尝试，这样我们就可以从这一点开始指导您；mysql_选择_dbb1396hos_数据库1或无法选择数据库$db->queryDELETE*从probid\u auction\u媒体删除，其中auction\u id不在probid\u auctions中，从probid\u auctions中选择不同的auction\u id；这似乎不起作用，这个的php版本是什么？

DELETE
FROM probid_auction_media
WHERE auction_id NOT IN(SELECT
                      probid_auction_media.auction_id
                    FROM probid_auctions,
                      probid_auction_media
                    where probid_auctions.auction_id != probid_auction_media.auction_id);