MySQL : GetFamilyTree

MySQL : GetFamilyTree

---------GET FAMILY TREE MYSQL CUSTOM FUNCTION------------------
 
DELIMITER $$
 
DROP FUNCTION IF EXISTS `GetChildren` $$
CREATE FUNCTION `GetChildren` (GivenID INT) RETURNS TEXT CHARSET latin1
DETERMINISTIC
BEGIN
 
    DECLARE rv,q,strq,queue,queue_children TEXT;
    DECLARE queue_length,front_id,pos,pos_que INT;
 
    SET rv = '';
    SET queue = GivenID;
    SET queue_length = 1;
 
    WHILE queue_length > 0 DO
    
    	IF LOCATE(',',queue)  = 0 THEN
            SET front_id = queue;
 		ELSE
            SET pos_que = LOCATE(',',queue);
            SET strq = SUBSTR(queue,1,pos_que);
            SET front_id = strq;
        END IF;
 
		IF queue_length = 1 THEN
            SET queue = '';
        ELSE
            SET pos = LOCATE(',',queue) + 1;
            SET q = SUBSTR(queue,pos);
            SET queue = q;
        END IF;
        SET queue_length = queue_length - 1;
 
        SELECT IFNULL(qc,'') INTO queue_children
        FROM (SELECT GROUP_CONCAT(id) qc
        FROM category WHERE parent_id = front_id) 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_children;
            ELSE
                SET rv = CONCAT(rv,',',queue_children);
            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 $$