Using DISTINCT in a joined subquery in MySQL - mysql

Question

Here is the fiddle for this question: http://sqlfiddle.com/#!9/0569eb/1
I have a table for comments, with replies stored in the same table as follows.
CREATE TABLE IF NOT EXISTS `comments` (
`id` int(6) unsigned NOT NULL,
`parent` int(3) unsigned NOT NULL,
`posted_by` int(3) unsigned NOT NULL,
`comment` varchar(200) NOT NULL,
`sort` int(3) NOT NULL,
PRIMARY KEY (`id`),
INDEX (`parent`),
INDEX (`posted_by`),
INDEX (`sort`)
) DEFAULT CHARSET=utf8;
INSERT INTO `comments` (`id`, `parent`, `posted_by`, `comment`, `sort`) VALUES
('1', '0', '1', 'Here is a comment by user 1', '5'),
('2', '1', '2', 'Here is a reply by user 2', '5'),
('3', '1', '3', 'Here is a reply by user 3', '5'),
('4', '1', '2', 'Here is a reply by user 2', '5'),
('5', '0', '2', 'Here is a comment by user 2', '2'),
('6', '0', '5', 'Here is a comment by user 5', '3');
I need to be able to select main comments that are posted by a user, or have a reply posted by that same user. The following is what I came up with to get the appropriate data for user 2.
Since there can be multiple replies on a single comment, I am using DISTINCT in a subquery to only get one reply per row. Is this an appropriate solution, or is there a better way to approach this situation?
SELECT
c.id,
c.comment
FROM comments c
LEFT JOIN (SELECT DISTINCT comments.parent FROM comments WHERE comments.posted_by = 2) r ON r.parent = c.id
WHERE
(
c.posted_by = 2
OR r.parent IS NOT NULL
)
AND c.parent=0
ORDER BY c.sort DESC;
The following is the expected output for comments relating to user 2

Answer 1

Edited: to remove the need for sort in the result as suggested in the comments
Nothing wrong with your solution, it works and is as concise as it can be.
As an alternative (but not better) you could use a UNION
SELECT id, comment
FROM (
SELECT
c.id,
c.comment,
c.sort
FROM comments c
WHERE posted_by = 2 AND parent = 0
UNION
SELECT DISTINCT
c.id,
c.comment,
c.sort
FROM comments c
JOIN comments p ON p.parent = c.id
WHERE p.posted_by = 2) x
ORDER BY sort DESC;