I already addressed something of this nature using Stored Procedures : Find highest level of a hierarchical field: with vs without CTEs (Oct 24, 2011)

If you look in my post, you could use the GetAncestry and GetFamilyTree functions as a model for traversing the tree from any given point.

UPDATE 2012-12-11 12:11 EDT

I looked back at my code from my post. I wrote up the Stored Function for you:

DELIMITER $$

DROP FUNCTION IF EXISTS `cte_test`.`GetFamilyTree` $$

CREATE FUNCTION `cte_test`.`GetFamilyTree`(GivenName varchar(64))

RETURNS varchar(1024) CHARSET latin1

DETERMINISTIC

BEGIN

    DECLARE rv,q,queue,queue_children,queue_names VARCHAR(1024);

    DECLARE queue_length,pos INT;

    DECLARE GivenSSN,front_ssn VARCHAR(64);

    SET rv = '';

    SELECT SSN INTO GivenSSN

    FROM Employee

    WHERE name = GivenName

    AND Designation <> 'OWNER';

    IF ISNULL(GivenSSN) THEN

        RETURN ev;

    END IF;

    SET queue = GivenSSN;

    SET queue_length = 1;

    WHILE queue_length > 0 DO

        IF queue_length = 1 THEN

            SET front_ssn = queue;

            SET queue = '';

        ELSE

            SET pos = LOCATE(',',queue);

            SET front_ssn = LEFT(queue,pos - 1);

            SET q = SUBSTR(queue,pos + 1);

            SET queue = q;

        END IF;

        SET queue_length = queue_length - 1;

        SELECT IFNULL(qc,'') INTO queue_children

        FROM

        (

            SELECT GROUP_CONCAT(SSN) qc FROM Employee

            WHERE MSSN = front_ssn AND Designation <> 'OWNER'

        ) A;

        SELECT IFNULL(qc,'') INTO queue_names

        FROM

        (

            SELECT GROUP_CONCAT(name) qc FROM Employee

            WHERE MSSN = front_ssn AND Designation <> 'OWNER'

        ) A;

        IF LENGTH(queue_children) = 0 THEN

            IF LENGTH(queue) = 0 THEN

                SET queue_length = 0;

            END IF;

        ELSE

            IF LENGTH(rv) = 0 THEN

                SET rv = queue_names;

            ELSE

                SET rv = CONCAT(rv,',',queue_names);

            END IF;

            IF LENGTH(queue) = 0 THEN

                SET queue = queue_children;

            ELSE

                SET queue = CONCAT(queue,',',queue_children);

            END IF;

            SET queue_length = LENGTH(queue) - LENGTH(REPLACE(queue,',','')) + 1;

        END IF;

    END WHILE;

    RETURN rv;

END $$

It actually works. Here is a sample:

mysql> SELECT name,GetFamilyTree(name) FamilyTree

    -> FROM Employee WHERE Designation <> 'OWNER';

+------+-----------------------+

| name | FamilyTree            |

+------+-----------------------+

| A    | B,F,C,H,L,I,K,D,E,G,J |

| G    |                       |

| D    |                       |

| E    |                       |

| B    | C,H,L,I,D,E,G,J       |

| F    | K                     |

| C    | D,E                   |

| H    | G                     |

| L    |                       |

| I    | J                     |

| K    |                       |

| J    |                       |

+------+-----------------------+

12 rows in set (0.36 sec)

mysql>

There is only one catch. I added one extra row for the owner

• The owner has SSN 0
• The owner is his own boss with MSSN 0

Here is the data

mysql> select * from Employee;

+-----+------+-------------+------+

| SSN | Name | Designation | MSSN |

+-----+------+-------------+------+

| 0   | A    | OWNER       | 0    |

| 1   | A    | BOSS        | 0    |

| 10  | G    | WORKER      | 5    |

| 11  | D    | WORKER      | 4    |

| 12  | E    | WORKER      | 4    |

| 2   | B    | BOSS        | 1    |

| 3   | F    | BOSS        | 1    |

| 4   | C    | BOSS        | 2    |

| 5   | H    | BOSS        | 2    |

| 6   | L    | WORKER      | 2    |

| 7   | I    | BOSS        | 2    |

| 8   | K    | WORKER      | 3    |

| 9   | J    | WORKER      | 7    |

+-----+------+-------------+------+

13 rows in set (0.00 sec)

mysql>

What you are using is called Adjacency List Model. It has a lot of limitations. You'll be problem when you want to delete/insert a node at a specific place. Its better you use Nested Set Model.

There is a detailed explanation. Unfortunately the article on mysql.com is does not exist any more.