QUESTION:
I have a simple MySQL table thats contains a list of categories, level is determined by parent_id:

id  name    parent_id
---------------------------
1   Home        0
2   About       1
3   Contact     1
4   Legal       2
5   Privacy     4
6   Products    1
7   Support     1

I'm attempting to make a breadcrumb trail. So i have the 'id' of the child, I want to get all available parents (iterating up the chain until we reach 0 "Home"). There could be any number or child rows going to an unlimited depth.
Currently I am using an SQL call for each parent, this is messy. Is there a way in SQL to do this all on one query?


ANSWER:
Adapted from here: https://explainextended.com/2009/07/20/hierarchical-data-in-mysql-parents-and-children-in-one-query/
For category "Privacy" (id=5):
----
SELECT T2.id, T2.name
FROM (
    SELECT
        @r AS _id,
        (SELECT @r := parent_id FROM table1 WHERE id = _id) AS parent_id,
        @l := @l + 1 AS lvl
    FROM
        (SELECT @r := 5, @l := 0) vars,
        table1 h
    WHERE @r <> 0) T1
JOIN table1 T2
ON T1._id = T2.id
ORDER BY T1.lvl DESC
----
The line @r := 5 is the ID for the current category. 
The result is as follows:
----
1, 'Home'
2, 'About'
4, 'Legal'
5, 'Privacy'

FOR MY TASK:
SELECT T2.id, T2.title
FROM (
    SELECT
        @r AS _id,
        (SELECT @r := parent_id FROM categories WHERE id = _id) AS parent_id,
        @l := @l + 1 AS lvl
    FROM
        (SELECT @r := 87, @l := 0) vars,
        categories h
    WHERE @r <> 0) T1
JOIN categories T2
ON T1._id = T2.id
ORDER BY T1.lvl DESC;