Get root path of a tree with pure MySQL - mysql

Question

I want to get path from node to root of a tree. This is my tree for example:
id | name | parent_id
------------------------------
1 | mike | 0
2 | danny | 1
3 | peter | 1
4 | clark | 2
5 | lily | 1
6 | stefan | 3
7 | simon | 3
8 | boby | 1
9 | john | 4
10 | elly | 4
I write an algoritm with php and mysql but it is slowly
public function GetRootPath($a_id) {
$root="";
$results="";
while(1==1){
$result = DB::select("SELECT id, parent_id FROM users WHERE id=$a_id");
if($result[0]->refr!=0) {
if($root==""){
$root=$result[0]->parent_id;
}
else {
$root=$result[0]->parent_id.'.'.$root;
}
$a_id=$result[0]->parent_id;
}
else {
break;
}
}
return $root;
}
How could this be written in pure MySQL? I'm not very aware with MySQL procedures and functions.

Answer 1

I think stored procedures could work:
DELIMITER $$
DROP PROCEDURE IF EXISTS get_root;
CREATE PROCEDURE get_root(
IN parentID INT,
OUT rootID INT
)
BEGIN
SELECT parent_id FROM tree WHERE id = parentID INTO rootID;
IF rootID = 0
THEN SET rootID = parentID;
ELSE
CALL get_root(rootID, rootID);
END IF;
END$$
DELIMITER ;
SET ##GLOBAL.max_sp_recursion_depth = 255;
SET ##session.max_sp_recursion_depth = 255;
CALL get_root(4, #rootID);
SELECT #rootID;