A file activation error occurred. The physical file name 'N@filename

Below t-sql code compiles fine. But when I run it like exec [SP_ATTACH_NW] 开发者_StackOverflow社区N'C:\myfolder' I get

Msg 5105, Level 16, State 2, Procedure SP_ATTACH_NW, Line 14 A file activation error occurred. The physical file name 'N@mdfFileName' may be incorrect. Diagnose and correct additional errors, and retry the operation.

USE master

GO

SET ANSI_NULLS ON

GO

CREATE PROCEDURE [dbo].[SP_ATTACH_NW] (
    @DestFolder varchar(255)
)

AS

BEGIN

    SET NOCOUNT ON;

    Declare @mdfFileName varchar(255)
    Declare @ldfFileName varchar(255)

    set @mdfFileName = @DestFolder + '\northwnd.mdf'
    set @ldfFileName = @DestFolder + '\northwnd.ldf'

CREATE DATABASE [Northwind] ON 

( FILENAME = N@mdfFileName ),

( FILENAME = N@ldfFileName )

 FOR ATTACH


END

Pls advise. thanks

---

You can't have variables in the filename arguments of CREATE DATABASE (MSDN doesn't show @vars in the syntax)

The code above is literally looking for the constant "N@mdfFileName" as a filename.

You'd need dynamic SQL to build a string in, say, @MyBuiltSQL then run EXEC(@MyBuiltSQL)

Note: The "N" prefix here would not make @mdfFileName nvarchar anyway