SQL轉換失敗錯誤

Question

WhenI調用這個存儲過程：

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       

我得到錯誤：

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

。

這是我怎麼稱呼SP：

DECLARE @return_value int 

EXEC @return_value = [dbo].[GetSorted] 

     @OrderByColumn = 'AddedBy' 


SELECT 'Return Value' = @return_value 

GO 

UPDATE： 如果我使用多情況下的做法，如拳頭2個答案建議， 嘗試添加另一種情況爲方向，當我得到的錯誤：

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

這裏是一個很好的文章，解釋您收到的錯誤：

Using CASE in ORDER BY clause

您可以將存儲過程改變以下是允許ORDER BY子句中的CASE工作（現在編輯爲包括訂單方向作爲參數）：

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

您試圖轉換數據類型，並且datetime具有更高的優先級。基本上「AddedBy =‘鮑勃’」無法轉換......

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