从多个日期中选择最大日期答案

【问题标题】：SELECT MAX DATE FROM MULTIPLE DATES从多个日期中选择最大日期
【发布时间】：2016-10-13 13:47:33
【问题描述】：

这是我的情况：

我有 2 张桌子 SKU 和 Disco_Dates。

在两个表中都有一个相似的字段。

SKU.[MFG_PART_NUMBER] = Disco_Dates.[MATERIAL]

我需要知道每个 MFG_PART_NUMBER 可用的最大 DATE_UPDATE

DISCO_DATE TABLE

+-------------+-----------------------+-----------------------+
| MATERIAL    |DISCO_DATE             | DATE_UPDATE           | 
+-------------+-----------------------+-----------------------+
|T6C25AW#ABC  |NULL                   |2016-09-14 11:15:03.587|
|T6C25AW#ABC  |2016-10-28 00:00:00.000|2016-09-21 13:45:03.591| 
|T6C25AW#ABC  |2016-10-31 00:00:00.000|2016-09-30 12:38:08.990| 
+-------------+-----------------------+-----------------------+

SKU TABLE

+---------------+
|MFG_PART_NUMBER| 
+---------------+
|T6C25AW#ABC    |
|G2F32UC#ABC    |
+---------------+

SQL查询

SELECT
 t1.[MFG_PART_NUMBER]
,t2.[DISCO_DATE]
,MAX (t2.[DATE_UPDATE]) as DATE_UPDATE

FROM Test.dbo.SKU t1

LEFT JOIN Test.dbo.Tbl_Disco_Dates t2
ON [MFG_PART_NUMBER] = [MATERIAL]

WHERE t1.[MFG_PART_NUMBER] = 'T6C25AW#ABC'

group by 
  t1.[MFG_PART_NUMBER]
 ,t2.[DISCO_DATE]

我当前的结果是全部 3 行。

这是我需要的。

+----------------+-----------------------+-----------------------+
|MFG_PART_NUMBER |DISCO_DATE             | DATE_UPDATE           |  
+----------------+-----------------------+-----------------------+
|T6C25AW#ABC     |2016-10-31 00:00:00.000|2016-09-30 12:38:08.990| 
+----------------+-----------------------+-----------------------+

提前致谢。

【问题讨论】：

标签： sql sql-server tsql

【解决方案1】：

试试这个：

SELECT
 t1.[MFG_PART_NUMBER]
,t2.[DISCO_DATE]
,t2.[DATE_UPDATE] as DATE_UPDATE

FROM Test.dbo.SKU t1

LEFT JOIN Test.dbo.Tbl_Disco_Dates t2
ON [MFG_PART_NUMBER] = [MATERIAL]

WHERE t1.[MFG_PART_NUMBER] = 'T6C25AW#ABC'
      AND t2.[DATE_UPDATE] = (SELECT MAX(t2.[DATE_UPDATE] FROM Test.dbo.Tbl_Disco_Dates t2)

【讨论】：

非常接近预期的结果。但这让我找到了答案 SELECT t1.[MFG_PART_NUMBER] ,t2.[DISCO_DATE] ,t2.[DATE_UPDATE] as DATE_UPDATE FROM Test.dbo.SKU t1 LEFT JOIN Test.dbo.Tbl_Disco_Dates t2 ON [MFG_PART_NUMBER] = [MATERIAL ] WHERE t1.[MFG_PART_NUMBER] = 'T6C25AW#ABC' AND t2.[DATE_UPDATE] = (SELECT MAX(t2.[DATE_UPDATE]) FROM Test.dbo.Tbl_Disco_Dates t2) group by t1.[MFG_PART_NUMBER] ,t2.[DISCO_DATE ] ,t2.[DATE_UPDATE]
哦，是的，我忘了 MAX 必须在 SELECT 语句中
这样操作还需要group by吗？
@Kris 好提示，不需要分组。

【解决方案2】：

 declare @maxdate datetime
 select @maxdate = max(t2.[DATE_UPDATE]) FROM Test.dbo.SKU
 select * from ( SELECT
  t1.[MFG_PART_NUMBER]
 ,t2.[DISCO_DATE]
  , DATE_UPDATE

  FROM Test.dbo.SKU  where DATE_UPDATE=   @maxdate)   t1 
  LEFT JOIN Test.dbo.Tbl_Disco_Dates t2
   ON t1.[MFG_PART_NUMBER] = t2.[MATERIAL]

  WHERE t1.[MFG_PART_NUMBER] = 'T6C25AW#ABC'

  group by 
 t1.[MFG_PART_NUMBER]
 ,t2.[DISCO_DATE]

【讨论】：

【解决方案3】：

一个简单的GROUP BY 查询不起作用：

SELECT MATERIAL,
       MAX(DISCO_DATE) AS DISCO_DATE,
       MAX(DATE_UPDATE) AS DATE_UPDATE
FROM Test.dbo.Tbl_Disco_Dates
GROUP BY MATERIAL

【讨论】：