EXEC sp_configure 'allow updates',1 RECONFIGURE WITH OVERRIDE

where id = object_id(@tablename) and name = @colname)
set @sql = 'alter table '+@tablename+' add '+@colname+' '+@coltype
--打开修改系统表的开关
--------------------------------------------------
--------------------------------------------------
--关闭修改系统表的开关
set @colid = @colid + 1
and name = '''+@colname +''''
if not exists(select 1 from sysobjects
@coltype varchar(100), --要加的列类型
and colid = '+cast(@colid_max as varchar(10))
--将其他列的列号加1
exec(@sql)
from syscolumns where id = object_id(@tablename) and name = @colname
raiserror 20002 '这个表已经有这个列了！'
@colname varchar(30), --要加的列名
where id = object_id('''+@tablename+''')
表示将id2这个列加到表test的第二个位置，类型是char(10)。
--------------------------------------------------
set @sql = 'update syscolumns
exec(@sql)
as
and colid >= '+cast(@colid as varchar(10))
exec(@sql)
调用方法：
if @@rowcount <> 1
exec(@sql)
--将新列列号暂置为-1
exec addcolumn '表名','新列名','新列类型',加到第几个位置
如：
@tablename varchar(30), --表名
where id = object_id('''+@tablename+''')
EXEC sp_configure 'allow updates',0 RECONFIGURE WITH OVERRIDE
if @colid > @colid_max or @colid < 1
declare @sql varchar(1000) --动态sql语句
set colid = '+cast(@colid as varchar(10))+'
--保证该表的colid是连续的
end
end
return -1


where id = object_id('''+@tablename+''')
if exists(select 1 from syscolumns
set @sql = 'update syscolumns
@colid int --加到第几列
begin
create proc addcolumn
return -1
select @colid_max = colid
--------------------------------------------------
end
raiserror 20001 '没有这个表'
begin
--------------------------------------------------
select @colid_max = max(colid) from syscolumns where id=object_id(@tablename)
set @sql = 'update syscolumns
--将新列列号复位

set colid = colid + 1
go
begin
return -1
raiserror 20003 '加一个新列不成功，请检查你的列类型是否正确'
declare @colid_max int
set colid = -1

--------------------------------------------------
where name = @tablename and xtype = 'u')
exec addcolumn 'test','id2','char(10)',2