我怎样才能拥有所有值的最大日期？

从表中的日期值（只显示前30名）

element      added     processed 
order-confirmation   2013-07-03 14:12:02 2013-07-03 14:12:03 
virtual-product-splitter 2013-07-03 14:12:02 2013-07-03 14:12:07 
fraud-protect   2013-07-03 14:12:02 2013-07-03 14:12:11 
giftcard-creator   2013-07-03 14:12:02 2013-07-03 14:12:15 
code-dispatcher   2013-07-03 14:12:02 0001-01-01 00:00:00 
order-confirmation   2013-07-03 14:10:01 2013-07-03 14:10:02 
virtual-product-splitter 2013-07-03 14:10:01 2013-07-03 14:10:06 
fraud-protect   2013-07-03 14:10:01 2013-07-03 14:10:10 
giftcard-creator   2013-07-03 14:10:01 2013-07-03 14:10:14 
code-dispatcher   2013-07-03 14:10:01 2013-07-03 14:10:19 
order-confirmation   2013-07-03 14:08:01 2013-07-03 14:08:02 
virtual-product-splitter 2013-07-03 14:08:01 2013-07-03 14:08:05 
fraud-protect   2013-07-03 14:08:01 2013-07-03 14:08:09 
giftcard-creator   2013-07-03 14:08:01 2013-07-03 14:08:13 
code-dispatcher   2013-07-03 14:08:01 2013-07-03 14:08:18 
code-dispatcher   2013-07-03 14:06:02 2013-07-03 14:06:19 
order-confirmation   2013-07-03 14:06:01 2013-07-03 14:06:02 
virtual-product-splitter 2013-07-03 14:06:01 2013-07-03 14:06:06 
fraud-protect   2013-07-03 14:06:01 2013-07-03 14:06:10 
giftcard-creator   2013-07-03 14:06:01 2013-07-03 14:06:14 
order-confirmation   2013-07-03 14:04:02 2013-07-03 14:04:03 
virtual-product-splitter 2013-07-03 14:04:02 2013-07-03 14:04:07 
fraud-protect   2013-07-03 14:04:02 2013-07-03 14:04:11 
giftcard-creator   2013-07-03 14:04:02 2013-07-03 14:04:15 
code-dispatcher   2013-07-03 14:04:02 2013-07-03 14:04:19 
order-confirmation   2013-07-03 14:02:01 2013-07-03 14:02:03 
virtual-product-splitter 2013-07-03 14:02:01 2013-07-03 14:02:06 
fraud-protect   2013-07-03 14:02:01 2013-07-03 14:02:10 
giftcard-creator   2013-07-03 14:02:01 2013-07-03 14:02:14 
code-dispatcher   2013-07-03 14:02:01 2013-07-03 14:02:19

做

select distinct element from sr_queue我得到

'c5-code-integration' 
'c5-debitor-integration' 
'c5-order-integration' 
'c5-product-integration' 
'code-dispatcher' 
'fraud-protect' 
'giftcard-creator' 
'order-confirmation' 
'packaged-confirmation' 
'virtual-product-splitter'

我试图附加最大日期（因为有几个）到每个元素，但做

select element, max(added), processed 
from sr_queue 
where element in (
    'c5-code-integration', 
    'c5-debitor-integration', 
    'c5-order-integration', 
    'c5-product-integration', 
    'code-dispatcher', 
    'fraud-protect', 
    'giftcard-creator', 
    'order-confirmation', 
    'packaged-confirmation', 
    'virtual-product-splitter')

我该如何创建选择？

这样我就可以得到：

order-confirmation   2013-07-03 14:12:02 2013-07-03 14:12:03 
virtual-product-splitter 2013-07-03 14:12:02 2013-07-03 14:12:07 
fraud-protect            2013-07-03 14:12:02 2013-07-03 14:12:11 
giftcard-creator            2013-07-03 14:12:02 2013-07-03 14:12:15 
code-dispatcher          2013-07-03 14:12:02 0001-01-01 00:00:00 
c5-code-integration   2013-07-03 14:12:02 2013-07-03 14:12:15 
...

我完全空白后第3天代码:(

来源

2013-07-03 balexandre

的MySQL，MS SQL Server的？ – Justin

select element, max(added), max(processed) 
from sr_queue 
group by element

编辑工作：

select element, added, processed 
from sr_queue q 
where added = (SELECT MAX(added) FROM sr_queue s WHERE s.element = q.element)

或者另一种可能性：

SELECT element, added, processed 
FROM sr_queue s 
INNER JOIN (
    SELECT element, MAX(added) 
    FROM sr_queue 
    GROUP BY element 
) q ON s.element = q.element

来源

2013-07-03 15:27:03 fancyPants

我想获得'max（added）'同一行的'processed'值，这可能吗？ – balexandre

当然，请参阅我编辑的答案。 – fancyPants

这在流程方面非常昂贵......需要找到更好的方法......在425000行中，需要超过10分钟：/ – balexandre

使用GROUP BY代替DISTINCT：

SELECT 
    element, 
    MAX(added) 
FROM 
    sr_queue 
GROUP BY 
    element

来源

2013-07-03 15:27:23 MarcinJuraszek

看，真的很累......“GROUP BY”arrghhhhhh！什么，等等......这样我就永远不会得到'MAX（已添加）'的'已处理'行，我该怎么做？ – balexandre

你使用什么数据库引擎？ SQL Server，MySQL，另外一个？ – MarcinJuraszek

目前的MySQL，但任何关系数据库应该工作... – balexandre

假设一个最新版本的MS SQL Server的

select element, added, processed from 
(select *, row_number() over (partition by element order by added desc) as ranker 
from sr_queue q) Z 
where ranker = 1

来源

2013-07-05 13:52:44 iruvar

我怎样才能拥有所有值的最大日期？

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