SQL 两列 guids 没有重复

Question

我正在通过观看 YouTube 来学习 SQL，我正在努力实现以下目标。我有一个 table 三列

Inspection Guid, SensorData Guid, DateTime

我想要 table Inspection Guid、SensorDataGuid、DateTime 但没有重复的 Inspection Guid。

来自（为方便起见，我缩短了 Guids）

6E814118    DA875776    2016-05-25 14:59:17.523
6E814118    BAEB255D    2016-05-25 14:59:17.523
4B7D4E90    BB717852    2016-05-25 14:58:46.260
06BB9435    2321EDD6    2016-05-25 14:58:16.870
06BB9435    D4168F8B    2016-05-25 14:58:16.870
8D9A8502    3EED26BE    2016-05-25 14:57:47.400
5C9AA885    77D342DD    2016-05-25 14:57:15.217
5C9AA885    43DEF213    2016-05-25 14:57:15.217

到

6E814118    DA875776    2016-05-25 14:59:17.523
4B7D4E90    BB717852    2016-05-25 14:58:46.260
06BB9435    2321EDD6    2016-05-25 14:58:16.870
8D9A8502    3EED26BE    2016-05-25 14:57:47.400
5C9AA885    77D342DD    2016-05-25 14:57:15.217

按日期时间排序。

非常感谢您的帮助。

Answer 1

使用ROW_NUMBER()根据DATE选择第一个GUID然后ORDER BY显示。

SELECT *
FROM (
        SELECT [Inspection Guid], 
               [SensorData Guid], 
               [DateTime],
               ROW_NUMBER() OVER (PARTITION BY [Inspection Guid] 
                                  ORDER BY [DateTime] DESC) rn
        FROM YourTable
      ) T
WHERE rn = 1
ORDER BY [DateTime] DESC

Answer 2

你要的其实问的不可以

以这2条记录为例：

06BB9435    2321EDD6    2016-05-25 14:58:16.870
06BB9435    D4168F8B    2016-05-25 14:58:16.870

如果您只想显示 06BB9435 一次，您会如何决定要显示其他哪些数据？您必须决定为每个重复的 GUID 显示哪个日期。如果您想要最近日期和按字母顺序排列最高的 SensorData，那么您可以这样做：

SELECT [Inspection Guid], MAX([SensorData Guid]), MAX([DateTime])
FROM YourTable
GROUP BY [Inspection Guid]
ORDER BY MAX([DateTime]) DESC

Answer 3

WITH duplicates AS
(
    SELECT
        [Inspection Guid],
        [SensorData Guid],
        [DateTime],
        ROW_NUMBER() OVER
        (
            PARTITION BY [Inspection Guid], [DateTime]
            ORDER BY [SensorData Guid]
        ) AS rn
    FROM YourTable
)
SELECT *
FROM duplicates
WHERE rn = 1

按 2 个字段 [Inspection Guid]、[DateTime] 的分区确保每个日期时间的分区都是唯一的。

SQL 两列 guids 没有重复

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