Question

I have a standard hierarchical table ID/PID and I need to find (boolean) if some child belongs to some ID. Is there a way to do this within mysql?

ID   PID
------------
1     0          <- root
...   ...
...   ... 
...   ...
7     1
...   ...
16    1
...   ...
4     0
...   ...
22    16
25    16

Is there a way to know if child node 22 belongs to node 1 ? I’m asking because I want to implement some Delete procedure, where node 1 is my Recycle. All deletes belongs to 1 will be deleted permanently and all other delete will have PID replaced, so temporarily belongs now to 1.

Thanks very much in advance,

Answer 1

Based on Hierarchical queries in MySQL :

SET @x := 22;
SET @y := 0;

select 'yes' as x_comes_from_y 
from dual
where @y in
(
 SELECT  @id :=
        (
        SELECT  pid
        FROM    h
        WHERE   id = @id
        ) AS nodes
 FROM    (
        SELECT  @id := @x
        ) vars
 STRAIGHT_JOIN
        h
 WHERE   @id IS NOT NULL
);

Test it.