Sql动态添加字段的正确姿势

SET ANSI_NULLS ONGOSET QUOTED_IDENTIFIER ONGO
-- =============================================
-- Author:<作者>
-- Create date: <20160320 Date,,>
-- Description:<当表插入数据时向相应的表增加列>
-- =============================================
ALTER TRIGGER [dbo].[Filed_Auto]  
 ON  [dbo].[Tbl_AutoFileds] for insert 
AS 
DECLARE@tb_Name varchar(50),
 @coloun varchar(50),
@datatype varchar(50),
@length varchar(1000),
@isnull varchar(10),
@sql varchar(200)BEGINSET NOCOUNT ON;  
select @tb_Name=tabld_name,@coloun=fieldName,@datatype=datatype,@length=[length],@isnull=[isnull] from inserted 
if not exists (select * from syscolumns where id=object_id(@tb_Name) and name=@coloun)   
begin
  set @sql=‘ALTER table ‘+@tb_Name+‘ add ‘+@coloun+‘ ‘+@datatype+‘(‘+@length+‘) ‘+@isnull
  exec (@sql)  
end

Insert into Tbl_AutoFields values(‘Tbl_Test‘,‘MyField‘,‘nvarchar‘,‘200‘,‘null‘);