MySQL Select Additional Rows on Same Table - mysql

Question

I am trying to return "parent" notes, where the from_person_id = 2. I would also like to return all of the "parent" note's child rows.
A "parent" note has a parent_note_id of 0.
A "child" note has a parent_note_id equal to its "parent" note's thread_note_id.
Both "parent" and "child" notes have the same thread_note_id.
Below is an example of 4 rows from the notes table. My query should be returning all 4 of these notes. Instead, it is only returning one.
mysql> SELECT * FROM notes WHERE note_id <= 4;
+---------+----------------+----------------+----------------+
| note_id | parent_note_id | thread_note_id | from_person_id |
+---------+----------------+----------------+----------------+
| 1 | 0 | 1 | 2 |
| 2 | 1 | 1 | 5 |
| 3 | 1 | 1 | 5 |
| 4 | 1 | 1 | 5 |
+---------+----------------+----------------+----------------+
4 rows in set (0.00 sec)
mysql> SELECT DISTINCT n.*
-> FROM notes as n
-> JOIN notes as n2 on n2.thread_note_id = n.thread_note_id
-> WHERE n.from_person_id = 2
-> AND n.parent_note_id = 0;
+---------+----------------+----------------+----------------+
| note_id | parent_note_id | thread_note_id | from_person_id |
+---------+----------------+----------------+----------------+
| 1 | 0 | 1 | 2 |
+---------+----------------+----------------+----------------+
1 row in set (0.00 sec)
I figured out a way to do it with two sub queries, but I am trying to avoid using sub queries in MySQL.
Anyone have a recommendation on how to get the query to return the parent note and all of its children using JOINs instead of Sub Queries?

Answer 1

I think you would do this as:
select n.*
from notes n
where n.parent_note_id = (select n2.note_id
from notes n2
where n2.from_person_id = 2
) or
n.from_person_id = 2;
For best performance, you want an index on notes(from_person_id, note_id).