CREATE TABLE FOO (
    id      NUMBER         NOT NULL
   ,name    VARCHAR2(20)
   ,parent  NUMBER
);

INSERT INTO FOO VALUES (1, 'First', NULL);
INSERT INTO FOO VALUES (2, 'Second 1', 1);
INSERT INTO FOO VALUES (3, 'Second 2', 1);
INSERT INTO FOO VALUES (4, 'Third', 2);

-- This is a formatting command
COLUMN id a40;

SELECT parent
      ,name
      ,LPAD(' ', 6*(Level - 1)) || id AS id
  FROM foo
 START WITH id = 1
CONNECT BY parent = PRIOR id;