3D array and sending emails for item once - php

Question

I have a checking script, it checks if the server/switch/router is alive.
The records are stored all in one db
CREATE TABLE IF NOT EXISTS `mod_monitoring` (
`id` int(11) NOT NULL,
`parentid` int(11) NOT NULL,
...
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
So a router could have a switch below it(connected via parent ID) and that could have a server under it, now if a server goes down, its fine because nothing would be under it and no double email would get sent out, however lets say a router goes out that has a router under it and a couple servers.
Because we check them all, we would send out emails for each item to the admin telling them each one is dead, but I need to send out only one email about the router going down. Hope that makes sense, I need to somehow only make an array of the IDs that have no children under it..
I could make an array of all the nodes that are down, but then how do I check if its the first one in the tree? and remove all the ones that are under it
Anyone could help? Been thinking about this for ages now!

Answer 1

If I understood what you want and that is iterate from parent to parent (which required a not specified number of JOIN), you need to use a Stored Procedure. Infact, to achieve this goal you need the Kleene closure that is not doable in a SQL query.

Answer 2

In the end I ended up making array of all the dead id's $key => $id
and then using the following
if(is_array($dead)) {
foreach($dead as $key => $id) {
$conn = $db->query("SELECT * FROM mod_monitoring WHERE id = {$id}");
$data = $db->fetch_array($conn);
if($data['parentid'] == 0) {
$final[] = $id;
unset($dead[$key]);
}
}
}
if(is_array($dead)) {
foreach($dead as $key => $id) {
$conn = $db->query("SELECT * FROM mod_monitoring WHERE id = {$id}");
$data = $db->fetch_array($conn);
if(in_array($data['parentid'], $final)) {
unset($dead[$key]);
}
if(in_array($id, $dead)) {
unset($dead[$key]);
}
}
}