Mysql 检索拍卖中每个项目的前2个出价

我无法合并多个表中的数据。我尝试过联接和子查询，但没有效果。我基本上需要将两个查询合并为一个查询。我的表格简化了：

股票：

id              int(9)      PrimaryIndex    
lot_number      int(4)
description     text     
reserve         int(9)
current_bid     int(9)
current_bidder  int(6)

成员:

member_id   int(11)         PrimaryIndex
name        varchar(255)

投标：

我目前使用两个单独的查询，有1000个批次，这使得它非常低效。第一个问题：

SELECT S.id, S.lot_number, S.description, S.reserve FROM stock S ORDER BY 
S.lot_number ASC

while循环中的第二个查询将获取投标信息：

SELECT DISTINCT B.bidder_id, B.lot_id, B.max_bid, B.time_of_bid,
M.fname, M.lname FROM bids B, members M WHERE B.lot_id=? AND
B.bidder_id=M.member_id ORDER BY B.max_bid DESC LIMIT 2

以下是我希望从单个查询中获得的输出（如果可能）：

Lot No. | Reserve | Current Bid | 1st Max Bid | 1st Bidder | 2nd Max Bid | 2nd Max Bidder

1       | $100    | $120        | $150        | Steve      | $110        | John
2       | $500    | $650        | $900        | Tom        | $600        | Paul

我只获得了MAXB.bid及其相关细节，其中S.id=B.id，但我无法获得每个批次的前2个出价。

首先将行号rn分配给表bids中每组批次id中的行，最高出价获得1，第二高出价获得2，依此类推。最高出价和第二高出价将在左联接后的两行上。使用GROUP BY将两行合并为一行

select  s.lot_number, s.reserve, s.current_bid, 
max( case when rn = 1 then b.max_bid end) as first_max_bid,
max( case when rn = 1 then m.name end) as first_bidder,
max( case when rn = 2 then b.max_bid end) as second_max_bid,
max( case when rn = 2 then m.name end ) as second_bidder
from 
stock s
left join
(select * from
  (select *,
   (@rn := if(@lot_id = lot_id, @rn+1,
              if( @lot_id := lot_id, 1, 1))) as rn
   from bids cross join
   (select @rn := 0, @lot_id := -1) param
   order by lot_id, max_bid desc
) t 
where rn <= 2) b
on s.lot_number = b.lot_id
left join members m 
on b.bidder_id = m.member_id
group by s.lot_number, s.reserve, s.current_bid
order by s.lot_number

---

你能在www.sqlfiddle.com上创建一个示例数据库并在此处共享链接吗？嗨，cdaiga，我试图创建你在此处要求的内容：如果有帮助，请告诉我。如果使用sqlfiddle.com/，似乎无法获得正确的数据！9/658272，虽然示例数据库可能不完整，因为我以前没有使用过该站点，因此可能需要进行一些改进，谢谢。@HeadbangA您在sqlfiddle中的测试数据确实不完整。很多出价在stock表中没有条目。这可能有点混乱，但是stock.id等同于bids.lot\u id不是bids.id，只是我的命名不一致。它似乎与您的示例中的一些小调整一起工作。这里的工作示例：sqlfiddle.com/！9/00cb8b/1

select  s.lot_number, s.reserve, s.current_bid, 
max( case when rn = 1 then b.max_bid end) as first_max_bid,
max( case when rn = 1 then m.name end) as first_bidder,
max( case when rn = 2 then b.max_bid end) as second_max_bid,
max( case when rn = 2 then m.name end ) as second_bidder
from 
stock s
left join
(select * from
  (select *,
   (@rn := if(@lot_id = lot_id, @rn+1,
              if( @lot_id := lot_id, 1, 1))) as rn
   from bids cross join
   (select @rn := 0, @lot_id := -1) param
   order by lot_id, max_bid desc
) t 
where rn <= 2) b
on s.lot_number = b.lot_id
left join members m 
on b.bidder_id = m.member_id
group by s.lot_number, s.reserve, s.current_bid
order by s.lot_number