delete child node when root node is deleted - PostgreSQL - postgresql

Question

I'm having a problem deleting child node. What I'm trying to do is that whenever a root node is deleted, it will also delete the child node. For example:
If I delete item 1, it should also delete item 2 automatically.
id: 1, name: item 1, parent_id: 0
id: 2, name: item 2, parent_d: 1
The id is PK and parent_id is FK.
I also created a sequence that when ever a new item is created, the id number increments by 1
sql command
DROP SCHEMA IF EXISTS note CASCADE;
CREATE SCHEMA note;
SET
search_path TO note;
CREATE TABLE note
(
id integer primary key,
name varchar(50),
parent_id integer references note.note (id) NOT NULL,
created_at timestamp without time zone DEFAULT now() NOT NULL
);
CREATE SEQUENCE note_id_seq
START WITH 1
INCREMENT BY 1
NO MINVALUE
NO MAXVALUE CACHE 1;
INSERT INTO note.note(id, name, parent_id)
VALUES
(1, 'item 1', 0)
,(2, 'item 2', 1)
SELECT SETVAL('note.note_id_seq',(SELECT MAX(id) FROM note.note))
Any suggestions would help a lot. Thanks!

Answer 1

You need to add on delete cascade to your foreign key:
CREATE TABLE note
(
id integer primary key,
name varchar(50),
parent_id integer references note (id) on delete cascade NOT NULL,
created_at timestamp without time zone DEFAULT now() NOT NULL
);
test it:
test=# insert into note(id,parent_id) values(0,0),(1,0),(2,1);
INSERT 0 3
test=# select (id,parent_id) from note;
row
-------
(0,0)
(1,0)
(2,1)
(3 rows)
test=# delete from note where id = 1;
DELETE 1
test=# select (id,parent_id) from note;
row
-------
(0,0)
(1 row)