Delete tree nodes from Table

Question

I have created a tree table
create table subforums (
id          NUMBER(5) primary key,
parent_id     references subforums,
name          varchar2(100)
And now i dont know how to delete a tree with a specified id and all of his children.
I tried to find out but i couldnt

Answer 1

Hi,
When you delete a node and all of its children, what do you want to do with the grandchildren? If you want to set their parent_id to NULL, do that in a separate UPDATE statement first, then DELETE the original node and all its remaining descendants, as show below.
If, when you say "children", you mean "descendants" (including
children,
children of children,
children of children of children,
and so on, to any level,
) then do a CONNECT BY query to find their primary keys, and DELETE everything in that list, like this:
DELETE  subforms
WHERE   id  IN
        SELECT  id
        FROM    subforms
        START WITH        id = :specified_id
        CONNECT BY  PRIOR id = parent_id
        );