can somebody help me with an update order?

i just need:
update topics set freigeschaltet = 0 where id = $URL{'id'}

i allready tried:

          $sql = SQL->new('topics');
          $sql->set('freigeschaltet');
          $sql->where('id');
          $sql->update('0',$URL{'id'});

but nothing helps
i never seen SUCH statements bevore and i do not know how to use them

/edit: you can close the post, i found out what was wrong
the right syntax is:

          $myid = $URL{'m'};
          $sql = SQL->new('topics','id');
          $sql->set('freigeschaltet');
          $sql->where('id');
          $sql->update(0,$myid);