即使我不希望它发生，列的更新也会发生

Question

我有一个案例陈述：

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

即使@AnsweredBy为NULL，它仍然会将AnsweredBy列设置为空。

我试图通过这样做来测试null：

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

含义除非有值，否则我不想更新answeredby列。

即使在我的C＃代码中，我也没有将值传递给我的存储过程：

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

除非有价值。在我的sproc中，我将该列变量默认为null：

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

所以我的问题是如何执行其余的更新，因为如果answeredby中有值，则只有5到10个列，但只更新@AnsweredBy？

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