嵌套Case語句在SQL查詢

Question

我的查詢

Declare  @From  DateTime='01 Feb 2013' 
Declare  @To   DateTime='28 Feb 2013 23:59:59' 

Select 
      Case 
        When 
        (
         Select TOP 1 f1.UpdatedOn 
         From TicketTypeFollowUp As f1 with(nolock) 
         Where f1.UpdatedOn<T.UpdatedOn And f1.Ticket=T.Ticket 
         Order By f1.UpdatedOn Desc 
       )IS Null 
        Then Ticket.TicketRaisedOn 

        Else 
        (
         Select TOP 1 f1.UpdatedOn 
         From TicketTypeFollowUp As f1 with(nolock) 
         Where f1.UpdatedOn<T.UpdatedOn And f1.Ticket=T.Ticket 
         Order By f1.UpdatedOn Desc 
       ) End [Start Date] 

     From dbo.TicketTypeFollowUp T with(nolock) 
     --Some Tables Omitted   
     Where CAST(TicketRaisedOn As Date)Between ''+Convert(VarChar(19), @From, 100)+''  And ''+Convert(VarChar(19), @To, 100)+'' 

如果列[Start Date]具有值大於@To然後@To值應打印否則[開始日期]列

我怎樣才能把它寫在相同的查詢？

我想什麼

 Case When(
      Case 
        When 
        (
         Select TOP 1 f1.UpdatedOn 
         From TicketTypeFollowUp As f1 with(nolock) 
         Where f1.UpdatedOn<T.UpdatedOn And f1.Ticket=T.Ticket 
         Order By f1.UpdatedOn Desc 
       )IS Null 
        Then Ticket.TicketRaisedOn 

        Else 
        (
         Select TOP 1 f1.UpdatedOn 
         From TicketTypeFollowUp As f1 with(nolock) 
         Where f1.UpdatedOn<T.UpdatedOn And f1.Ticket=T.Ticket 
         Order By f1.UpdatedOn Desc 
       ) End [Start Date] 
      )> @To Then @To Else [Start Date] End, 

DB：SQL SERVER 2008

Answer 1

它看起來對我來說，你需要這樣的：

Declare  @From  DateTime='01 Feb 2013' 
Declare  @To   DateTime='28 Feb 2013 23:59:59' 

Select CASE WHEN ISNULL(StartDates.[Start Date], Ticket.TicketRaisedOn) > @To THEN @To ELSE ISNULL(StartDates.[Start Date], Ticket.TicketRaisedOn) END AS ResultValue 
From dbo.TicketTypeFollowUp T with(nolock) 
    --Some Tables Omitted 
    OUTER APPLY 
    (
     Select TOP 1 f1.UpdatedOn AS [Start Date] 
     From TicketTypeFollowUp As f1 with(nolock) 
     Where f1.UpdatedOn<T.UpdatedOn And f1.Ticket=T.Ticket 
     Order By f1.UpdatedOn Desc 
    ) StartDates 
Where CAST(TicketRaisedOn As Date)Between ''+Convert(VarChar(19), @From, 100)+''  And ''+Convert(VarChar(19), @To, 100)+'' 

外應用用於指定每行一個計算值，從上面的連接表中引用值，但在那之後它就像來自JOIN的數據。所以你給你的APPLY一個別名，就像它是一個表一樣，然後根據需要多次訪問它的值。

正如你所看到的，這大大簡化了您的query--適用是非常方便的在你的工具帶。）））

編輯新增根據註釋另一ISNULL。