來自Case語句的冗餘行並加入SQL Server

Question

我收到了一些重複的case case語句。

如何避免使用子查詢？

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) 

注意我只想用1

Answer 1

這些都不是重複的，他們是從多行Audit導致單獨的記錄行 - 在你的例子一個用OldValue_Text「服務檯「，而不是。

現在，如果你只是尋找1當現在和0否則，你可以做的三兩件事之一：

1. 保留現有的查詢，並把你的第三列的最大值：

   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] 
   

2. 使用EXISTS與相關子查詢（我知道你說你不希望使用一個，但是這是一個有效的解決方案）：

   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] 
   

3. 將條件OldValue_Text = 'Service Desk'添加到join子句中。這將減少連接的行到你以後的行。 （注意：這裏假設只有一個匹配行;如果沒有，你可能需要添加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

你的case語句是SELECT子句中，因此它不會給你重複。這些也不是重複的，它們是完全不同的記錄。我相信所有你需要做的就是添加一個where子句，只有拉記錄與「服務檯」

WHERE [A].OldValue_Text LIKE 'Service Desk' 

您會在FROM子句，但你的組之前by子句後添加此的OldValue_Text。

這將減少你的結果設置爲僅具有對Moved from old Board?

值1項。如果這讓你重複的，那麼你可以只添加一個distinct到您的SELECT子句

SELECT DISTINCT 

     [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?'