Question

我正在尝试根据一组software_image_build_id and variant

获取最大时间戳行

这是我的SQL小提琴链接http://sqlfiddle.com/#!9/6ed643/1，它应该为software_image_build_id和variant的组合输出最大时间戳行，我尝试如下但是没有帮助，任何人都可以提供有关如何修复它的指导吗？

SELECT software_image_build,MAX(timestamp) FROM software_image_builds where software_image_id=1452
group by software_image_build

Answer 1

您需要使用内部查询来获取数据以及最大时间戳，然后使用外部查询通过software_image_id和variant获取数据，以确保您获得具有最大时间戳的正确数据。

SELECT OUTSIDE.*
FROM software_image_builds OUTSIDE, 
   (SELECT software_image_id, variant, MAX(timestamp) as maxtimestamp
    FROM software_image_builds
    GROUP BY software_image_id, variant) AS INSIDE
WHERE OUTSIDE.software_image_id = INSIDE.software_image_id
AND OUTSIDE.variant = INSIDE.variant
AND OUTSIDE.timestamp = INSIDE.maxtimestamp

Answer 2

结果似乎正确，你想要什么结果？这个sql获取software_image_build和每个software_image_build的最大时间戳。

如果要获取所有数据的最大时间戳，请不要使用group by。

SELECT software_image_build,MAX(timestamp) FROM software_image_builds where software_image_id=1452

如果您想获取每个software_image_build，并将每行的最大时间戳拆分，请尝试以下查询：

SELECT S.software_image_build,A.max_timestamp 
FROM software_image_builds AS S,
(SELECT software_image_build,MAX(timestamp) as max_timestamp 
  FROM software_image_builds where software_image_id=1452) 
  AS A
group by S.software_image_build

输出：

software_image_build            max_timestamp
CI_LA.UM.5.8-02200-8x98.1-16    2017-07-14T21:51:02Z
CI_LA.UM.5.8-02200-8x98.1-20    2017-07-14T21:51:02Z
CI_LA.UM.5.8-60402-8x98.1-1     2017-07-14T21:51:02Z

Answer 3

您现在发布的SQL：

SELECT software_image_build,max(timestamp)
FROM software_image_builds
WHERE software_image_id=1452
GROUP BY software_image_build,variant
LIMIT 1

输出：

software_image_build            timestamp
CI_LA.UM.5.8-02200-8x98.1-16    2017-07-13T18:38:41Z
CI_LA.UM.5.8-02200-8x98.1-20    2017-07-14T21:51:02Z
CI_LA.UM.5.8-60402-8x98.1-1     2017-02-28T15:08:10Z

这似乎正是你现在所说的你想要的。如果没有，则需要进一步澄清。

Answer 4

试试这个

SELECT * FROM software_image_builds where software_image_id=1452 
   AND timestamp = (SELECT MAX(timestamp) as timestamp from  
  software_image_builds 
 where software_image_id=1452)

检查小提琴http://sqlfiddle.com/#!9/729532/44

Answer 5

select * from software_image_builds where timestamp in（SELECT MAX（timestamp）来自software_image_builds group by software_image_id，variant）;

Answer 6

您可以按时间戳列对结果进行排序，然后使用limit仅返回第一个结果。

SELECT software_image_build, timestamp FROM software_image_builds where
software_image_id=1452 group by software_image_build order by timestamp DESC     
limit 1

如何从给定表中获取最大时间戳行

6 个答案: