Question

我在Microsoft SQL Server 2008中有一个数据库

我有一个表[eventlog].[dbo].[USER_OPERATION]，其中包含[userID], [event_description], [event_date], [event_type], [eventID]列

eventID对于每一个可能发生的特定事件都是独一无二的。

给定的UserID当然不是唯一的事件（每个用户可能有很多与他相关的事件）但与单个用户相关联

我想要的是创建一个查询，该查询会为我提供一个列表，其中只包含每个用户的最新事件（也就是说，每个UserID）及其相关信息（特定事件的event_type，eventID和event_description。

举例说明：

执行时

SELECT * 
FROM [eventlog].[dbo].[USER_OPERATION] 
ORDER BY userID ASC

我得到的是

|====================================================================================|
|  eventID  |  userID  |        event_description        |  event_date  | event_type |
|           |          |                                 |              |            |
|   123     |    2     |  USER 2 broke something         |  03.11.11    |   CRASH    |
|   391     |    2     |  USER 2 filed a complaint       |  30.04.10    |  COMPLAINT |
|   392     |    2     |  USER 2 has bought beer         |  31.10.09    |  PURCHASE  |
|   32      |    3     |  USER 3 broke something         |  22.10.11    |   CRASH    |
|   568     |    4     |  USER 4 has requested support   |  05.12.11    |  SUPP_REQ  |
|   691     |    4     |  USER 4 has bought beer         |  01.12.10    |  PURCHASE  |
|   81      |    4     |  USER 4 updated personal data   |  17.07.11    |  PDAT_UPD  |
|   141     |    5     |  USER 5 has bought beer         |  16.08.11    |  PURCHASE  |
|   142     |    5     |  USER 5 broke something         |  16.08.11    |   CRASH    |
|   269     |    6     |  USER 6 updated personal data   |  27.01.12    |  PDAT_UPD  |
|   845     |    7     |  USER 7 updated personal data   |  27.01.12    |  PDAT_UPD  |
|           |          |                                 |              |            |
|====================================================================================|

如您所见，某些用户拥有多个与其关联的日期不同的事件。

我想要的是一个查询，它会显示一个用户列表以及用户有一个事件的最新日期（输出本质上是一个列出每个用户一次的表，并显示最新的与每个用户关联的事件，以及关联的event_description，event_date和event_type info）。

我们将这样的查询结果称为“最近事件表”。

请注意用户5（用户ID 5）在同一天破坏并买啤酒的“异常情况”。

在这种情况下，我不关心两个当天事件中的哪一个会进入“最近事件表”，它可以随机选择或其他任何事情（虽然我仍然需要关联的event_description和event_type信息。）

理想情况下，结果看起来像这样（对于同一组用户）：

|====================================================================================|
|  eventID  |  userID  |        event_description        |  event_date  | event_type |
|           |          |                                 |              |            |
|   123     |    2     |  USER 2 broke something         |  03.11.11    |   CRASH    |
|   32      |    3     |  USER 3 broke something         |  22.10.11    |   CRASH    |
|   568     |    4     |  USER 4 has requested support   |  05.12.11    |  SUPP_REQ  |
|   141     |    5     |  USER 5 has bought beer         |  16.08.11    |  PURCHASE  |
|   269     |    6     |  USER 6 updated personal data   |  27.01.12    |  PDAT_UPD  |
|   845     |    7     |  USER 7 updated personal data   |  27.01.12    |  PDAT_UPD  |
|           |          |                                 |              |            |
|====================================================================================|

如果没有办法“随机选择两个中的任何一个或按照某些规则”为用户5选择“日期欺骗”，在“最近事件表”中有两个条目“对于这种特殊情况是可以接受的，因为它们非常罕见，我可以手动处理它们。

在这种（稍微不那么幸运）的情况下，“近期事件表”看起来像

|====================================================================================|
|  eventID  |  userID  |        event_description        |  event_date  | event_type |
|           |          |                                 |              |            |
|   123     |    2     |  USER 2 broke something         |  03.11.11    |   CRASH    |
|   32      |    3     |  USER 3 broke something         |  22.10.11    |   CRASH    |
|   568     |    4     |  USER 4 has requested support   |  05.12.11    |  SUPP_REQ  |
|   141     |    5     |  USER 5 has bought beer         |  16.08.11    |  PURCHASE  |
|   142     |    5     |  USER 5 broke something         |  16.08.11    |   CRASH    |
|   269     |    6     |  USER 6 updated personal data   |  27.01.12    |  PDAT_UPD  |
|   845     |    7     |  USER 7 updated personal data   |  27.01.12    |  PDAT_UPD  |
|           |          |                                 |              |            |
|====================================================================================|

这也是可以接受的（但稍后需要进行一些额外的修剪）。

那么，总结一下我的问题，是否有可能构建一个这样的Microsoft SQL查询，它会给我一个与上述内容一致的最近事件表？

非常感谢您的帮助

Answer 1

您可以将CTE（公用表表达式）与ROW_NUMBER()函数结合使用：

;WITH CTE AS 
(
    SELECT  
       *,
       RowNum = ROW_NUMBER() OVER (PARTITION BY UserID 
                                   ORDER BY event_date DESC, event_id DESC)
    FROM [eventlog].[dbo].[USER_OPERATION] 
)
SELECT *
FROM CTE
WHERE RowNum = 1

将您的数据“划分”为多个组 - 每个UserID一个 - 然后按event_date DESC和event_id DESC对该数据组内的事件进行排序并对其进行编号 - 最近的条目（对于每个用户）获得RowNum = 1 - 所以只需从CTE中选择那些就完成了！

Answer 2

DECLARE @USER_OPERATION table 
(
eventID int,
userID int,
event_description nvarchar(250),
event_date date,
event_type nvarchar(250)
)
Insert into @USER_OPERATION values  (123,2,'USER 2 broke something','11/03/11','CRASH')
Insert into @USER_OPERATION values  (391,2,'USER 2 filled a complaint','04/30/10','COMPLAINT')
Insert into @USER_OPERATION values  (392,2,'USER 2 bought beer','10/31/09','PURCHASE')
Insert into @USER_OPERATION values  (32,3,'USER 3 broke something','10/22/11','CRASH')
Insert into @USER_OPERATION values  (568,4,'USER 4 has requested support','12/05/11','SUPP_REQ')
Insert into @USER_OPERATION values  (691,4,'USER 4 has bought beer','12/01/10','PURCHASE ')
Insert into @USER_OPERATION values  (81,4,'USER 4 updated personal data','07/17/11','PDAT_UPD ')
Insert into @USER_OPERATION values  (141,5,' USER 5 has bought beer','08/16/11','PURCHASE')
Insert into @USER_OPERATION values  (142,5,' USER 5 broke something','08/16/11','CRASH')
Insert into @USER_OPERATION values  (269,6,'USER 6 updated personal data','01/27/12','PDAT_UPD')
Insert into @USER_OPERATION values  (845,7,'USER 7 updated personal data ','01/27/12','PDAT_UPD')


SELECT * FROM @USER_OPERATION AS userOp INNER JOIN
(SELECT DISTINCT userID, (SELECT Top 1 eventID FROM @USER_OPERATION a WHERE a.userID  =B.userID ORDER BY event_date DESC)as eventID
from @USER_OPERATION AS B) as tbl 
ON userOp.userID =tbl.userID and userOp.eventID =tbl.eventID

如何在Microsoft SQL Server 2008中为给定用户选择最新事件？

2 个答案: