Increase the depth of an MySQL query

Question

public function get_children($id)
{
        $query = $this->db->query("SELECT 
          @last_id := id AS id,
          parent_id,
          FIO,
          @depth := IF(parent_id = ".$id.", 1, @depth + 1) AS depth,
          @first := IF(id = ".$id.", 'first', null) AS first
          FROM 
          users 
          FORCE INDEX (index_parent_id, PRIMARY, index_both),
          (SELECT @last_id := ".$id.", @depth := -1) vars
          WHERE id = ".$id." OR parent_id = @last_id OR parent_id = ".$id."
          ");

    return $query;

}

How can i increase the level depth of children nodes using the adjacent-model-list and this query, by now it gives me the root parent(selected by id in the function) and their children, but not deeper, any ideas?

foreach($query->result() as $q){


    if($q->first == 'first')
    {
        $parent_id = $q->parent_id;
        break;
    }


}
function print_list($array, $parent=0) {
        print "<ul>";
        foreach ($array as $row) {
            if ($row->parent_id == $parent) {
                print "<li>$row->FIO";
                print_list($array, $row->id);  # recurse
                print "</li>";
        }   }
        print "</ul>";
    }
echo print_list($query->result(), $parent_id);

then I render it in the view file...please help or any advices about what to change or see to increase the depth of the mysql query.

Answer 1

I'm not sure about the schema of the database, but this is basically a stripped down version of something you might be looking for. Basically, you'll need a function that calls itself, but the argument changes.

In this case, it looks for users with parent_id = $parent_id (assuming the parent_id of the root is 0) lists then, and for each of the users, it looks for other users with parent_id = $id (where $id is their id) so basically, you have infinite depth

<?
function print_list($parent_id) {
    $query = "SELECT * FROM users WHERE parent_id=".$parent_id;

    print "<ul>";
    foreach($query->result() as $q) {
        $id = $q->id;
        print "<li>";
            print $q->FIO;
        print "</li>";
        print_list($id); //Here, it calls itself again
    }
    print "</ul>";
}
print_list(0); //Assuming the root-parent-id number is 0