使用MAX和GROUP BY选择所有相应的字段

Question

我有这张桌子:

我想提出,将返回每个请求deal_id具有最高的行timestamp,并相应status_id.

所以对于这个例子,我会返回2行:

1226, 3, 2009-08-18 12:10:25
1227, 2, 2009-08-17 14:31:25

我尝试用这个查询来做

SELECT deal_id, status_id, max(timestamp) FROM deal_status GROUP BY deal_id

但它会回错status_id:

1226, 1, 2009-08-18 12:10:25
1227, 1, 2009-08-17 14:31:25

Answer 1

没有一个主键字段,我认为你最好的选择是:

select * from deal_status
inner join
  (select deal_id as did, max(timestamp) as ts
  from deal_status group by deal_id) as ds
  on deal_status.deal_id = ds.did and deal_status.timestamp = ds.ts

如果您允许同时为同一产品提供两种不同的状态,这仍然不起作用