本文介绍了使用MAX和GROUP BY选择所有对应的字段的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有这张表：
我想要为每个 deal_id 返回最高 timestamp ，和相应的 status_id 。
因此，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我试图用这个查询来完成它。
SELECT deal_id，status_id，max（timestamp）FROM deal_status GROUP BY deal_id但它会返回错误的 status_id ：
1226，1，2009-08-18 12:10:25 1227,1，2009-08-17 14:31 ：25解决方案
你最好的选择是：
select * from dea l_status 在deal_status.deal_id = ds.did和deal_status中，内部连接（选择deal_id，max（时间戳）作为ts from deal_status group by deal_id）作为ds 。 timestamp = ds.ts如果您允许两个不同的状态产品在同一时间
I have this table :
And I would like to make a request that would return for each deal_id the row with the highest timestamp, and the corresponding status_id.
So for this example, I would have returned 2 rows :
1226, 3, 2009-08-18 12:10:25 1227, 2, 2009-08-17 14:31:25I tried to do it with this query
SELECT deal_id, status_id, max(timestamp) FROM deal_status GROUP BY deal_idbut it would return the wrong status_id :
1226, 1, 2009-08-18 12:10:25 1227, 1, 2009-08-17 14:31:25解决方案
without a single primary key field, I think your best bet is:
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.tsthis still won't work if you allow having two different statuses for the same product at the same time
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使用MAX和GROUP BY选择所有对应的字段
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