SQL转换失败错误

Question

WhenI调用这个存储过程：

ALTER PROCEDURE [dbo].[GetSorted] 
(
    @OrderByColumn nvarchar(256) 

) 
AS 
SET NOCOUNT ON  

    SELECT itDocs.AddedDate, itDocs.AddedBy FROM itDocs  
    ORDER BY 
      CASE WHEN @OrderByColumn='AddedDate' THEN itDocs.AddedDate 
        WHEN @OrderByColumn='AddedBy' THEN itDocs.AddedBy 

     END ASC       

我得到错误：

Conversion failed when converting date and/or time from character string

。

这是我怎么称呼SP：

DECLARE @return_value int 

EXEC @return_value = [dbo].[GetSorted] 

     @OrderByColumn = 'AddedBy' 


SELECT 'Return Value' = @return_value 

GO 

UPDATE： 如果我使用多情况下的做法，如拳头2个答案建议， 尝试添加另一种情况为方向，当我得到的错误：

ORDER BY 
     CASE WHEN @OrderDirection=0 THEN    
      CASE WHEN @OrderByColumn='AddedDate' THEN itDocs.AddedDate END ASC, 
      CASE WHEN @OrderByColumn='AddedBy' THEN itDocs.AddedBy END ASC  
     end  
     CASE WHEN @OrderDirection=1 THEN 

Answer 1

这里是一个很好的文章，解释您收到的错误：

Using CASE in ORDER BY clause

您可以将存储过程改变以下是允许ORDER BY子句中的CASE工作（现在编辑为包括订单方向作为参数）：

ALTER PROCEDURE [dbo].[GetSorted] 
(
    @OrderByColumn nvarchar(256), 
    @OrderDirection int 
) 
AS 
SET NOCOUNT ON    
    SELECT itDocs.AddedDate, itDocs.AddedBy FROM itDocs   
     ORDER BY    
     CASE WHEN @OrderByColumn='AddedDate' AND @OrderDirection=0 THEN itDocs.AddedDate END ASC, 
     CASE WHEN @OrderByColumn='AddedBy' AND @OrderDirection=0 THEN itDocs.AddedBy END ASC,   
     CASE WHEN @OrderByColumn='AddedDate' AND @OrderDirection=1 THEN itDocs.AddedDate END DESC, 
     CASE WHEN @OrderByColumn='AddedBy' AND @OrderDirection=1 THEN itDocs.AddedBy END DESC 

Answer 2

您试图转换数据类型，并且datetime具有更高的优先级。基本上“AddedBy =‘鲍勃’”无法转换......

SELECT 
    itDocs.AddedDate, itDocs.AddedBy 
FROM 
    itDocs  
ORDER BY 
    CASE OrderByColumn WHEN 'AddedDate' THEN itDocs.AddedDate ELSE '19000101' END, 
    CASE OrderByColumn WHEN 'AddedBy' THEN itDocs.AddedBy ELSE '' END