Question

我有一个小型的竞价系统，我正用于幻想拍卖。我正在尝试使用以下查询来提取每个玩家的最高出价。但是，它实际上并没有给我最高出价，只是给了我输入数据库的第一个。

SELECT Bid.id FROM bids AS Bid 
WHERE Bid.active =1
GROUP BY player_id HAVING MAX( Bid.amount )

以下是Bid表格布局，如果有帮助：

CREATE TABLE IF NOT EXISTS `bids` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `user_id` int(10) NOT NULL,
  `player_id` int(10) NOT NULL,
  `amount` int(6) NOT NULL,
  `timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `winning_bid` int(1) NOT NULL DEFAULT '0',
  `active` int(1) NOT NULL DEFAULT '1',
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 ;

Answer 1

select max(amount), player_id from bids 
 where active = 1
 group by player_id
 order by 1 desc;

Answer 2

Ever子句需要进行布尔检查。所以，你的having MAX(Bid.Amount)并没有按照你的想法去做。你（理论上）想要的是having Bid.Amount = MAX(Bid.Amount)，虽然这会导致更多问题，因为你应该在技术上对Bid.Amount进行分组，因为它存在于聚合之外，而这根本不是你的意思。

（警告，未经测试的查询，但它们应该非常接近）

如果您只想要单个玩家的最高出价，那么您实际应该做的非常简单，按出价按降序排序时选择第一条记录：

select
  b.id
from
  bids b
where
  b.active = 1
  and b.player_id = @playerID
order by
  b.bids desc
limit 1

如果你想要所有玩家，这个查询仍然给你起点，你只需要将每个player_id传递给它：

select
  bid.playerID,
  bid.id
from
  bids bid
  join (
    select
      b.id
    from
      bids b
    where
      b.active = 1
    order by
      b.bids desc
    limit 1
  ) maxbid on maxbid.playerid = bid.playerid

Answer 3

你可以尝试：

SELECT Bid.id
  FROM bids AS Bid,
       (SELECT player_id, MAX(amount) AS player_max
          FROM bids
          WHERE active=1
          GROUP BY player_id) AS max_amounts
  WHERE Bid.player_id = max_amounts.player_id
    AND Bid.amount = max_amounts.amount;

但是，我不确定在发生关系时的行为。

Answer 4

或者，Khorkrak的另一种选择（其中也可以使用）：

SELECT Bid.id FROM bids AS Bid 
LEFT JOIN bids as x
ON x.amount > Bid.amount
AND x.active = 1
AND x.player_id = Bid.player_id
WHERE Bid.active = 1 AND x.player_id IS NULL
GROUP BY player_id

Answer 5

这是一个使用行级来查找最高出价的人。你也可以使用这样的东西来找到第二高，第三高等......


SELECT id, player_id, amount 
FROM 
( 
select b.id, b.player_id, b.amount, count(*) as num 
from bids b left outer join bids b2 
on b.player_id = b2.player_id 
AND b.amount = b2.timestamp 
AND b.active = 1 
group by b.id, b.player_id, b.amount 
)
r 
WHERE
num = 1

MySQL查询：获胜拍卖出价

5 个答案: