如何用SQL语句在指定字段前面插入新的字段？

转载自http://www.cnblogs.com/ringnet/archive/2007/04/24/724935.html

create proc addcolumn

@tablename varchar(30), --表名

@colname varchar(30), --要加的列名

@coltype varchar(100), --要加的列类型

@colid int --加到第几列

as

declare @colid_max int

declare @sql varchar(1000) --动态sql语句

--------------------------------------------------

if not exists(select 1 from sysobjects

where name = @tablename and xtype = 'u')

begin

raiserror 20001 '没有这个表'

return -1

end

--------------------------------------------------

if exists(select 1 from syscolumns

where id = object_id(@tablename) and name = @colname)

begin

raiserror 20002 '这个表已经有这个列了！'

return -1

end

--------------------------------------------------

--保证该表的colid是连续的

select @colid_max = max(colid) from syscolumns where id=object_id(@tablename)

if @colid > @colid_max or @colid < 1

set @colid = @colid + 1

--------------------------------------------------

set @sql = 'alter table '+@tablename+' add '+@colname+' '+@coltype

exec(@sql)

select @colid_max = colid

from syscolumns where id = object_id(@tablename) and name = @colname

if @@rowcount <> 1

begin

raiserror 20003 '加一个新列不成功，请检查你的列类型是否正确'

return -1

end

--------------------------------------------------

--打开修改系统表的开关

EXEC sp_configure 'allow updates',1 RECONFIGURE WITH OVERRIDE

--将新列列号暂置为-1

set @sql = 'update syscolumns

set colid = -1

where id = object_id('''+@tablename+''')

and colid = '+cast(@colid_max as varchar(10))

exec(@sql)

--将其他列的列号加1

set @sql = 'update syscolumns

set colid = colid + 1

where id = object_id('''+@tablename+''')

and colid >= '+cast(@colid as varchar(10))

exec(@sql)

--将新列列号复位

set @sql = 'update syscolumns

set colid = '+cast(@colid as varchar(10))+'

where id = object_id('''+@tablename+''')

and name = '''+@colname +''''

exec(@sql)

--------------------------------------------------

--关闭修改系统表的开关

EXEC sp_configure 'allow updates',0 RECONFIGURE WITH OVERRIDE

go

调用方法：

exec addcolumn '表名','新列名','新列类型',加到第几个位置

如：

exec addcolumn 'test','id2','char(10)',2

表示将id2这个列加到表test的第二个位置，类型是char(10)。