修改用户定义的数据类型

--SQLSERVER的自定义类型比较好用吧，但是，一旦引用该数据类型后，想修改数据类型，就是一大头疼的事了，本存储过程就是专门对付它的。

--sp_rebuildallview 见本BLOG中的其它页面[color=#3f3d3d]
[/color]create procedure sp_rechangfieldtype(@typename varchar(50), @newtype varchar(50))
as
begin declare @typeid int
declare @tablename varchar(50)
declare @column varchar(50)
declare @sqlstr varchar(200)
declare @defaultid int

select @typeid = xusertype
from systypes
  where name = @typename and xusertype > 256
  AND (is_member('db_owner') = 1 OR is_member('db_ddladmin') = 1 OR is_member(user_name(uid))=1)
declare mycursor cursor for
select o.name, c.name, c.cdefault
from syscolumns c, systypes t, sysusers u, sysobjects o
where c.xusertype = @typeid
and t.xusertype = @typeid
and o.uid = u.uid
and c.id = o.id
  and o.type = 'u'
open mycursor
fetch next from mycursor into @tablename, @column, @defaultid
while @@fetch_status = 0
begin
  if @defaultid <> 0
  begin
    set @sqlstr = 'alter table ' + @tablename + ' drop ' + object_name(@defaultid)
    exec(@sqlstr)
    set @sqlstr = 'alter table ' + @tablename + ' alter column ' + @column + ' ' + @newtype
    exec(@sqlstr)
   
--    set @sqlstr = 'alter table ' + @tablename + ' add contraint ' + @tablename + [color=#3f3d3d]'df'+@column[/color] + ' default 0'
  end
  else
  begin
    set @sqlstr = 'alter table ' + @tablename + ' alter column ' + @column + ' ' + @newtype
    print @sqlstr
    exec(@sqlstr)
  end
  --if @@error <> 0
  --  continue
  fetch next from mycursor into @tablename, @column, @defaultid
end
--如果没有约束，则可以直接删除。如果有约束。先处理约束。
close mycursor
deallocate mycursor
end

GO

create procedure SP_CHANGEFIELD(@OLDTYPENAME VARCHAR(50), @NEWDTYPE VARCHAR(50))
as
begin
  exec('sp_addtype U_LOCALTYPE, ''' + @newdtype + '''')
  exec SP_rechangfieldtype @OLDTYPENAME, 'U_LOCALTYPE'
  EXEC sp_rebuildallview
  EXEC('sp_droptype ' + @OLDTYPENAME)
  EXEC('sp_addtype ' + @OLDTYPENAME + ', ''' + @newdtype + '''')
  exec SP_rechangfieldtype 'U_LOCALTYPE', @OLDTYPENAME
  EXEC sp_rebuildallview
  EXEC sp_droptype 'U_LOCALTYPE'
end
GO

--以下是示例。将U_HELLO的长度改为 30

SP_ADDTYPE U_HELLO, 'VARCHAR(10)'
GO
CREATE TABLE TESTTYPE(NAME U_HELLO)
GO
SP_CHANGEFIELD 'U_HELLO', 'VARCHAR(30)'