如果在sql中構建

Question

我不擅長t-sql，所以我需要幫助。

我有這樣的代碼，我寫我自己，但怎麼寫，我想我不知道（與英語難過）

declare @questionid int 
set @questionid = 22 

declare @providerid int 
set @providerid = 189 

select [closed] into #question from [Data].[dbo].[Question] where [questionid] = @questionid 

-- and here, if [closed] is null I must write in the question table current date GETDATE() 
UPDATE [Data].[dbo].[Question] SET [closed] = GETDATE() WHERE [questionid] = @questionid and [providerid] = @providerid 

-- or, if [closed] is not null I must write there null 
UPDATE [Data].[dbo].[Question] SET [closed] = null WHERE [questionid] = @questionid and [providerid] = @providerid 

drop table #question 

我怎麼能這樣做？

Answer 1

你並不需要爲這個

declare @questionid int 
set @questionid = 22 

declare @providerid int 
set @providerid = 189 

declare @closed datetime 
select @closed = [closed] from [Data].[dbo].[Question] where [questionid] = @questionid 

-- and here, if [closed] is null I must write in the question table current date GETDATE() 
IF @closed IS NULL 
    UPDATE [Data].[dbo].[Question] SET [closed] = GETDATE() WHERE [questionid] = @questionid and [providerid] = @providerid 
ELSE 
-- or, if [closed] is not null I must write there null 
    UPDATE [Data].[dbo].[Question] SET [closed] = null WHERE [questionid] = @questionid and [providerid] = @providerid 

我必須說，我不明白你正在努力實現的邏輯臨時表...

Answer 2

利用case when可以輕鬆實現你的任務..

UPDATE [Data].[dbo].[Question] 
SET [closed] = CASE 
      WHEN [closed] is null THEN GetDate() 
      ELSE null 
      END 
WHERE [questionid] = @questionid 
    and [providerid] = @providerid