Question

我的案例陈述中有一些重复。

如何在不使用子查询的情况下避免这种情况？

SELECT  

  [S].[TicketNbr] AS 'Ticket Nbr'
, [S].[status_description] AS 'Status'
, ( CASE  WHEN [A].OldValue_Text = 'Service Desk' THEN 1  ELSE 0  END) AS 'Moved from Old Board?' END) AS 'Moved from Old Board?'

FROM [Service] AS [S]
LEFT OUTER JOIN [Audit] AS [A]   
ON [A].[TicketNbr]=[S].[TicketNbr]

GROUP BY [S].[TicketNbr]
, [S].[status_description]
,(CASE  WHEN [A].OldValue_Text = 'Service Desk' THEN 1  ELSE 0  END)

注意我只希望行为1。

Answer 1

这些不是重复的，它们是由Audit中的多行产生的单独记录 - 在您的示例中，OldValue_Text为“服务台”，而另一个则不是。{/ p>

现在，如果你只是在寻找1，而在0，你可以做以下三件事之一：

保留现有查询并占用第三列的最大值：

SELECT      
  [S].[TicketNbr] AS [Ticket Nbr],
  [S].[status_description] AS [Status],
  MAX((CASE WHEN [A].OldValue_Text = 'Service Desk' THEN 1 ELSE 0  END)) AS [Moved from Old Board?]

FROM [Service] AS [S]
LEFT OUTER JOIN [Audit] AS [A]   
  ON [A].[TicketNbr]=[S].[TicketNbr]

GROUP BY [S].[TicketNbr],
  [S].[status_description]

将EXISTS与相关子查询一起使用（我知道你说你不想使用它，但这是一个有效的解决方案）：

SELECT      
  [S].[TicketNbr] AS [Ticket Nbr],
  [S].[status_description] AS [Status],
  CASE WHEN EXISTS (SELECT 1 FROM [Audit] AS [A]   
    WHERE [A].[TicketNbr]=[S].[TicketNbr]
    AND [A].OldValue_Text = 'Service Desk') THEN 1 ELSE 0 END AS [Moved from Old Board?]

FROM [Service] AS [S]

将条件OldValue_Text = 'Service Desk'添加到join子句中。这会将连接的行减少到您所追求的行。（注意这假设只有一行匹配;如果不匹配，则可能需要添加DISTINCT）：

SELECT      
  [S].[TicketNbr] AS [Ticket Nbr],
  [S].[status_description] AS [Status],
  CASE WHEN [A].[TicketNbr] IS NOT NULL THEN 1 ELSE 0 END AS [Moved from Old Board?]

FROM [Service] AS [S]
LEFT OUTER JOIN [Audit] AS [A]   
  ON [A].[TicketNbr]=[S].[TicketNbr]
  AND [A].OldValue_Text = 'Service Desk'

Answer 2

您的case语句位于select子句中，因此它不会给您重复。这些也不是重复，它们是完全不同的记录。我相信你需要做的就是添加一个where子句，只用OldValue_Text“Service Desk”来拉取记录

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您可以在from子句之后但在group by子句之前添加它。

这会将结果集减少为仅WHERE [A].OldValue_Text LIKE 'Service Desk'

值为1的项目

如果这给你重复，那么你可以在你的select子句中添加Moved from old Board?

distinct

Case语句中的冗余行和加入SQL Server

2 个答案: