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create table comments_table (
id int,
reply_to_id int,
content varchar(20)
);
insert into comments_table values
(12, NULL, 'TEXT'),
(13, 12, 'TEXT'),
(14, 12, 'TEXT'),
(15, 13, 'TEXT');
Records: 4 Duplicates: 0 Warnings: 0
WITH recursive cte (id, reply_to_id, path)
AS
(
SELECT id, reply_to_id, CAST(id AS CHAR(200)) AS path
FROM comments_table
WHERE reply_to_id = 12
UNION ALL
SELECT e.id, e.reply_to_id, CONCAT(cte.path, ",", e.id)
FROM comments_table AS e
JOIN cte ON e.reply_to_id = cte.id
)
SELECT *
from cte
order by path
| id | reply_to_id | path |
|---|---|---|
| 13 | 12 | 13 |
| 15 | 13 | 13,15 |
| 14 | 12 | 14 |