sub query tabel yang sama

query.sql

-- create schema
CREATE TABLE users (
  id int not null primary key auto_increment,
  name varchar(50) not null,
  parent_id int null default null
);

-- insert data
INSERT INTO users (id, name, parent_id) VALUES
(1, 'Zaki', 2),
(2, 'Ilham', NULL),
(3, 'Irwan', 2),
(4, 'Arka', 3);

-- query
SELECT 
  u.id, 
  u.name, 
  (
    SELECT su.name FROM users su WHERE id = u.parent_id
  ) AS parent_name
FROM users u