--開啟系統表寫功能以便創建存儲過程
EXEC sp_configure 'allow updates',1 
RECONFIGURE WITH OVERRIDE
GO

CREATE PROC sp_addColumn
@TableName sysname,              --要添加字段的表名
@FieldDefine nvarchar(1000),   --要添加的列的定義,定義必須符合ALTER TABLE tbname ADD規范
@Position   int=-1                --添加列位置,其值為1~表的總列數,比如1,表示添加為第1列,
                                        如果@Position無效,則僅添加列
AS
IF ISNULL(OBJECTPROPERTY(OBJECT_ID(@TableName),'IsUserTable'),0)=0
BEGIN
	RAISERROR(N'無效的表名 "%s"',12,16,@TableName)
	return
END

--添加字段
DECLARE @s nvarchar(4000)
SET @s=N'ALTER TABLE '+QUOTENAME(@TableName)+N' ADD '+@FieldDefine

BEGIN TRAN
	EXEC sp_executesql @s
	IF @@ERROR=0
	BEGIN
		DECLARE @maxcolid int
		SELECT @Position=ISNULL(@Position,0),@maxcolid=MAX(colid) 
		FROM syscolumns
		WHERE id=OBJECT_ID(@TableName)
		IF @Position>0 AND @Position<@maxcolid
			UPDATE syscolumns SET 
				colid=CASE colid WHEN @maxcolid THEN @Position ELSE colid+1 END,
				colorder=CASE colid WHEN @maxcolid THEN @Position ELSE colid+1 END
			WHERE id=OBJECT_ID(@TableName)
				AND colid>=@Position
		COMMIT TRAN
	END
	ELSE
		ROLLBACK TRAN
GO

--關閉系統表寫功能
EXEC sp_configure 'allow updates',1 
RECONFIGURE WITH OVERRIDE