Obtenha o caminho raiz de uma árvore com MySQL puro

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;