Question

我正在尝试获取特定商品的最高出价，并显示出价该金额的用户

我能够通过两个不同的查询获得结果，每个查询返回我想要的子集

select username, auctionbids.itemid, description, bidamt from AuctionBids 
inner join users on auctionbids.userid = users.id
inner join auctionitems on auctionbids.itemid = auctionitems.itemid

select ab.itemid,max(ab.bidamt) as bidmax from auctionbids as ab group by ab.itemid

我想获取用户名，itemid，item描述符，max（bidamt）连接到三个表-用户，拍卖品，拍卖出价。

用户包含用户名和用户名

拍卖项目包含项目ID和项目说明

拍卖标书包含用户ID，物品ID，比阿姆特

Answer 1

以下查询应执行您想要的操作：

SELECT a.item_description,a.username,a.bidamt FROM 
(
SELECT au.item_description,u.username,ab.bidamt, RANK() OVER(PARTITION BY au.itemid ORDER BY ISNULL(ab.bidamt,0) DESC) AS [Rank]
FROM auctionitems au
LEFT JOIN auctionbids ab ON au.itemid = ab.itemid
LEFT JOIN users u ON ab.userid = u.userid ) a WHERE [Rank] = 1

Answer 2

正如您所说，两个不同的查询每个都返回您想要的子集，您的查询应该像这样：

SELECT am.username, am.itemid, am.descripton, max(am.bidamt) AS bidmax
FROM (
    SELECT username, auctionbids.itemid, auctionitems.description, bidamt FROM AuctionBids 
    INNER JOIN users ON auctionbids.userid = users.id
    INNER JOIN auctionitems ON auctionbids.itemid = auctionitems.itemid
) AS am 
GROUP BY am.itemid

Answer 3

没有示例数据，就无法验证其是否正常工作。但是您需要将bidamt与MAX bidamt与特定项目进行匹配。

SELECT DISTINCT
    users.username,
    auctionbids.itemid,
    auctionitems.description,
    auctionbids.bidamt

FROM
    users
        INNER JOIN auctionbids on users.userid = auctionbids.userid
        INNER JOIN auctionitems on auctionbids.itemid = auctionitems.itemid

WHERE
    auctionbids.bidamt = (SELECT MAX(bidamt) OVER (PARTITION BY itemid, description))
    AND
    itemid = < whatever you want >

Answer 4

感谢导致此查询的想法-

SELECT am.*, auctionbids.submitted, users.username, auctionitems.description 
FROM
(SELECT ab.itemid, max(ab.bidamt) as bidmax 
FROM 
auctionbids ab
GROUP BY ab.itemid) AS am
   INNER JOIN auctionbids ON am.itemid = auctionbids.itemid and am.bidmax = auctionbids.bidamt
    INNER JOIN users ON auctionbids.userid = users.id
    INNER JOIN auctionitems ON auctionbids.itemid = auctionitems.itemid

因此，基本上，必须在itemid上通过group by找到最大值，然后与其余表进行内部联接以获取属性。

查询以查找具有多个分组依据属性的值的最大值

4 个答案: