将列名动态传递给 SQL 查询

Question

我想知道是否可以传递表的列名，以便为我的存储过程创建动态查询。我将不胜感激！

很好的查询：

SELECT
A1,
LEFT (A1,CHARINDEX(',',A1)-1) AS UPC,
SUBSTRING(A1,CHARINDEX(',', A1 , 1)  + 1,LEN(A1) - CHARINDEX(',', A1) - CHARINDEX(',', REVERSE(A1))) AS Date,
SUBSTRING(A1,CHARINDEX(',', A1 , 1)  + 7,LEN(A1) - CHARINDEX(',', A1) - CHARINDEX(',', REVERSE(A1))) AS Qty
FROM Registry Where Id=26

输出：

 A1              UPC      Date    Qty
-------------------------------------
CPU1,01/15,3     CPU1     01/15   3

这就是我目前所拥有的存储过程

SP：

ALTER PROCEDURE [dbo].[SP_UPD_Compartment] 
@Id  int, 
@Col_Name char(40) 

AS
BEGIN
SET NOCOUNT ON;

SELECT
@Col_Name,
LEFT (@Col_Name,CHARINDEX(',',@Col_Name)-1) AS UPC,
SUBSTRING(@Col_Name,CHARINDEX(',', @Col_Name , 1)  + 1,LEN(@Col_Name) - CHARINDEX(',', @Col_Name) - CHARINDEX(',', REVERSE(@Col_Name))) AS Date,
SUBSTRING(@Col_Name,CHARINDEX(',', @Col_Name , 1)  + 7,LEN(@Col_Name) - CHARINDEX(',', @Col_Name) - CHARINDEX(',', REVERSE(@Col_Name))) AS Qty
FROM Registry Where Id=@Id

END

错误信息：

Msg 537, Level 16, State 2, Procedure SP_UPD_Compartment, Line 9
Invalid length parameter passed to the LEFT or SUBSTRING function.

Answer 1

我是从制表符输入的，所以可能有一些语法错误，但我想你会明白的。首先，您使用语句创建一个字符串，然后将子字符串“@Col_Name”替换为传递给过程的参数。然后你执行那个动态sql。您还可以在EXEC(@cmd) 之前添加Print @cmd 以查看实际将执行的内容。

ALTER PROCEDURE [dbo].[SP_UPD_Compartment] 
@Id  INT, 
@Col_Name CHAR(40) 

AS
BEGIN
SET NOCOUNT ON;

DECLARE @cmd NVARCHAR(4000) =
'SELECT
@Col_Name,
LEFT (@Col_Name,CHARINDEX('','',@Col_Name)-1) AS UPC,
SUBSTRING(@Col_Name,CHARINDEX('','', @Col_Name , 1)  + 1,LEN(@Col_Name) - CHARINDEX('','', @Col_Name) - CHARINDEX('','', REVERSE(@Col_Name))) AS Date,
SUBSTRING(@Col_Name,CHARINDEX('','', @Col_Name , 1)  + 7,LEN(@Col_Name) - CHARINDEX('','', @Col_Name) - CHARINDEX('','', REVERSE(@Col_Name))) AS Qty
FROM Registry WHERE Id=' + CAST(@Id AS NVARCHAR(20))

SET @cmd = REPLACE(@cmd, '@Col_Name', @Col_Name)
EXEC(@cmd)

END