Finding all parents in mysql table with single query (Recursive Query)
I have this schema
Sample Data
| ID | TITLE | CONTROLLER | METHOD | PARENT_ID |
|----|-------------------|------------|-------------------|-----------|
| 1 | Dashboard | admin | dashboard | 0 |
| 2 | Content | admin | content | 0 |
| 3 | Modules | admin | modules | 0 |
| 4 | Users | admin | users | 0 |
| 5 | Settings | admin | settings | 0 |
| 6 | Reports | admin | reports | 0 |
| 7 | Help | admin | help | 0 |
| 8 | Pages | content | pages | 2 |
| 9 | Media | content | media | 2 |
| 10 | Articles | content | articles | 2 |
| 11 | Menues | content | menues | 2 |
| 12 | Templates | content | templates | 2 |
| 13 | Themes | content | themes | 2 |
| 14 | Blog | content | blog | 2 |
| 15 | Forum | content | forum | 2 |
| 16 | Core Modules | modules | core_module | 3 |
| 17 | User Modules | modules | user_module | 3 |
| 18 | All Users | users | all_users | 4 |
| 19 | Groups | users | groups | 4 |
| 20 | Permissions | users | permissions | 4 |
| 21 | Import and Export | users | import_export | 4 |
| 22 | Send Email | users | send_mail | 4 |
| 23 | Login Records | users | login_records | 4 |
| 24 | General Settings | settings | general_settings | 5 |
| 25 | Email Settings | settings | email_settings | 5 |
| 26 | Popular Content | reports | popular_content | 6 |
| 27 | Most Active Users | reports | most_active_users | 6 |
| 28 | Documentation | help | documentation | 7 |
| 29 | About | help | about | 7 |
| 30 | Products | products | product | 17 |
| 31 | Categories | categories | category | 17 |
SQL Fiddle demo.I have inserted some sample data.
Challange
I need to find all the parents of the record where the title is Categories. How can I get all the parents with only a single query?
I mean I need this result:
Desired Output
id | title | controller | method | url | parent_id
----------------------------------------------------------------
3 | Modules | admin | modules | (NULL) | 0
17 | User Modules | modules | user_module | (NULL) | 3
31 | Categories | categories | category | (NULL) | 17
Let suppose I want to fetch an entry with all of its parent and I want to use the where condition id = 31, it should fetch above records.
Answer
SELECT T2.id, T2.title,T2.controller,T2.method,T2.url
FROM (
SELECT
@r AS _id,
(SELECT @r := parent_id FROM menu WHERE id = _id) AS parent_id,
@l := @l + 1 AS lvl
FROM
(SELECT @r := 31, @l := 0) vars,
menu m
WHERE @r <> 0) T1
JOIN menu T2
ON T1._id = T2.id
ORDER BY T1.lvl DESC;