drop table node;
create table node (
       id number primary key
      ,op varchar2(2)
      ,value number
      ,parent references node
      ,parse varchar2(50)
      ,carry number
);

insert into node values (1,'*' ,NULL,NULL,NULL,NULL);
insert into node values (2,'+' ,NULL,1   ,NULL,NULL);
insert into node values (3,'-' ,NULL,1   ,NULL,NULL);
insert into node values (4,NULL,1   ,2   ,NULL,NULL);
insert into node values (5,NULL,3   ,2   ,NULL,NULL);
insert into node values (6,NULL,4   ,2   ,NULL,NULL);
insert into node values (7,NULL,4   ,3   ,NULL,NULL);
insert into node values (8,NULL,5   ,3   ,NULL,NULL);

drop view pnode;
drop view enode;

create view enode as (
  select n.id,n.op,n.value,n.parent,n.carry
  from node n left outer join node p on n.parent = p.id
  where n.carry is null
  and   p.carry is null
 UNION
  select n.id,NULL,n.carry,n.parent,n.carry
  from node n left outer join node p on n.parent = p.id
  where n.carry is not null
  and   p.carry is null
);

create view pnode as (
  select n.id,n.op,cast(n.value as varchar2(50)) value,n.parent,n.parse
  from node n left outer join node p on n.parent = p.id
  where n.parse is null
  and   p.parse is null
 UNION
  select n.id,NULL,n.parse,n.parent,n.parse
  from node n left outer join node p on n.parent = p.id
  where n.parse is not null
  and   p.parse is null
);