postgresql - update tree table with rows from same table by changing id andparent_id

Question

I have 2 tables:

\\d folder

                              Table \"public.folder\"
Column   |         Type          |                             


        

Answer 1

why do not use simple update ?

BEGIN;
UPDATE folder
SET    parent_id = 3
WHERE  id        = 5;

UPDATE files
SET    folder_id = 3
WHERE  folder_id = 5;
END;