学步园

declare @t table(id int identity(1,1),tbname varchar(256), colname varchar(256),xtype varchar(20))
insert into @t
select a.name,b.name ,c.name
from sysobjects a
    inner join syscolumns  b on a.id=b.id
    inner join systypes  c on b.xusertype = c.xusertype 
where a.xtype='u'
  and c.name in ('varchar','int')
  and b.status<>0x80  --去掉自增列  
  and not exists  --过滤掉原来已存在默认值的列
     (select 1
      from
          (select
                (select name from sysobjects where id=c.id) 表名,
                (select name from syscolumns where cdefault=a.id) 字段名
           from  sysobjects b,syscolumns c,syscomments a
           where b.xtype='d'
             and a.id=b.id
             and b.parent_obj=c.id
             and a.colid=c.colid
           ) t
      where a.name=t.表名
        and b.name=t.字段名)
--select * from @t
declare @i int
set @i=1
declare @tbname varchar(256),@colname varchar(256),@xtype varchar(20),@sql nvarchar(4000)
while @i <= (select MAX(id) from @t)
begin
    select @tbname=tbname,@colname=colname,@xtype = xtype from @t where id=@i
    set @sql = 'alter table ['+@tbname+'] add constraint ' +  'df_' + replace(@tbname,'-','') +'_'+ replace(@colname,'-','') + ' default '
    if @xtype = 'int'
    begin
        set @sql = @sql + ' 0 '
    end
    else if @xtype = 'varchar'
    begin
        set @sql = @sql + ''''''
    end
    set @sql = @sql + ' for [' + @colname +']'
    exec(@sql)
    set @i = @i + 1
end

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