SQL Query on recursive table

Question

I have a to do a request on a "recursive table".

Please find below an example

ID    |    FATHER_ID    |    NAME
100   |    0            |  Human
101   |    0            |  Car
102   |    101          |  PORSCHE
103   |    101          |  AUDI
104   |    102          |  911
105   |    102          |  MACAN
106   |    103          |  A3
107   |    103          |  A5
...   |    ...          |

I would like to get something like

PARENT_NAME   |   NAME
PORSCHE       | 911
PORSCHE       | MACAN
AUDI          | A3
AUDI          | A5
...           | ...

I'm able to go to the first level with below query:

SELECT ID, FATHER_ID, NAME FROM LISTS WHERE FATHER_ID IN (SELECT ID FROM LISTS WHERE NAME = 'Car')


ID   |   FATHER_ID   |    NAME
102  | 101           | PORSCHE  
103  | 101           | AUDI

But is it possible to go to the level 2 (car model) by keeping level 1 information (the brand)?

I able to get information of level 2 with below query. But I'm losing brand name.

SELECT ID, FATHER_ID, NAME FROM LISTS WHERE FATHER_ID IN (SELECT ID FROM LISTS WHERE FATHER_ID IN (SELECT ID FROM LISTS WHERE NAME = 'Car'))

Thank you in advance

Regards

Answer 1

Walk the tree building a cumulative string as you go, then filter the result to keep only the deepest level

With FullTree as (
    Select ID, '' as Names, 0 as Level
    From Lists
    Where Father_ID = 0
  Union All
    Select ID, f.Names + ' | ' + c.Name as Names, f.level+1 as Level
    From Lists c inner join FullTree f on c.Father_ID = f.ID
)
Select Names from FullTree 
Where Level = (Select max(Level) From FullTree)
Order by Names

If you wish, you can trim the left part of the string to remove the initial vertical bar.

Answer 2

You can walk the tree in reverse, starting at the lowest level.

WITH cte AS (
    SELECT l.ID, l.FATHER_ID, l.NAME
    FROM LISTS l
    WHERE NOT EXISTS (SELECT 1
        FROM LISTS child
        WHERE child.FATHER_ID = l.ID)

    UNION ALL

    SELECT parent.ID, parent.FATHER_ID, CONCAT(parent.NAME, '|', child.NAME)
    FROM LISTS parent
    JOIN cte child ON child.FATHER_ID = l.ID
)
SELECT l.NAME
FROM cte
WHERE cte.FATHER_ID IS NULL;   -- this line removes intermediate levels