--删除所有约束  
DECLARE c1 cursor for  
    select 'alter table ['+ object_name(parent_obj) + '] drop constraint ['+name+']; '  
    from sysobjects  
    where xtype = 'F'  
open c1  
declare @c1 varchar(8000)  
fetch next from c1 into @c1  
while(@@fetch_status=0)  
    begin  
        exec(@c1)  
        fetch next from c1 into @c1  
    end  
close c1  
deallocate c1  
--删除数据库所有表  
declare @tname varchar(8000)  
set @tname=''  
select @tname=@tname + Name + ',' from sysobjects where xtype='U'  
select @tname='drop table ' + left(@tname,len(@tname)-1)  
exec(@tname)