update node set parse = (
select o.op||'('||l1.value||')'
from pnode o,pnode l1
where o.id = l1.parent
and   node.id = o.id
and   not exists (
      select o2.id from pnode o2
      where o2.parent = o.id
      and   o2.value is null
      and   o2.parse is null)
and   (select count(*) from pnode oo,pnode ll1
       where oo.id = ll1.parent
       and   o.id = oo.id
      ) = 1
UNION
select o.op||'('||l1.value||','||l2.value||')'
from pnode o,pnode l1,pnode l2
where o.id = l1.parent
and   o.id = l2.parent
and   l1.id < l2.id
and   node.id = o.id
and   not exists (
      select o2.id from pnode o2
      where o2.parent = o.id
      and   o2.value is null
      and   o2.parse is null)
and   (select count(*) from pnode oo,pnode ll1
       where oo.id = ll1.parent
       and   o.id = oo.id
      ) = 2
UNION
select o.op||'('||l1.value||','||l2.value||','||l3.value||')'
from pnode o,pnode l1,pnode l2,pnode l3
where o.id = l1.parent
and   o.id = l2.parent
and   o.id = l3.parent
and   l1.id < l2.id
and   l2.id < l3.id
and   node.id = o.id
and   not exists (
      select o2.id from pnode o2
      where o2.parent = o.id
      and   o2.value is null
      and   o2.parse is null)
and   (select count(*) from pnode oo,pnode ll1
       where oo.id = ll1.parent
       and   o.id = oo.id
      ) = 3
) where parse is null
;