更新列的是即使我不希望它發生

Question

我有一個case語句：

UPDATE 
    Answer 
SET 
    AnswerID = @AnswerID, 
    AnsweredBy = CASE WHEN LEN(@AnsweredBy) > 0 THEN @AnsweredBy END 

即使@AnsweredBy是NULL它仍然設置AnsweredBy列設置爲空。

我試着做這個測試空以及：

UPDATE 
    Answer 
SET 
    AnswerID = @AnswerID, 
    AnsweredBy = CASE WHEN @AnsweredBy IS NOT NULL THEN @AnsweredBy END 

含義我不想更新answeredby列，除非有一個值。除非有一個值

if (answeredBy.Length > 0) 
    cmdSelect.Parameters.Add("@AnsweredBy", SqlDbType.VarChar).Value = answeredBy; 

：

即使在我的C＃代碼我沒有一個值傳遞給我的存儲過程。而在我的存儲過程我默認該列變量設置爲null：

@RunoffAnswerID bigint, 
@AnswerID varchar(3)=NULL, 
@AnsweredBy varchar(50)=NULL, 

所以我的問題是我如何執行我的其餘更新，因爲有大約5-10多列，但如果只更新answeredby@AnsweredBy的值？

Answer 1

SET AnsweredBy = ISNULL(@AnsweredBy, AnsweredBy) 

Answer 2

UPDATE 
    Answer 
SET 
    AnswerID = @AnswerID, 
    AnsweredBy = CASE WHEN LEN(@AnsweredBy) > 0 THEN @AnsweredBy ELSE AnsweredBy END