Problem with MySQL nested cursors - mysql

Question

I have the following bunch of code trying to update a field using 2 cursors the one inside the other. I use the first cursor just to get an id value (1st cursor) and then I get a list of other id values based on that id (2nd cursor). The problem is that the result set from the 2nd cursor contains the last id twice! I can't find the bug! Something in the loop, something in the termination variable for the 2 cursors?
Any help more than welcome! Thanks in advance!
DELIMITER $$
DROP PROCEDURE IF EXISTS updateNumberOfPoisForPlacesWithChildren$$
CREATE PROCEDURE updateNumberOfPoisForPlacesWithChildren()
BEGIN
DECLARE single_place_id INT(11);
DECLARE single_unique_parents_id INT(11);
DECLARE done, temp_number_of_pois, sum_number_of_pois INT DEFAULT 0;
DECLARE unique_parents_ids CURSOR FOR SELECT DISTINCT `parent_id` FROM `places` WHERE `parent_id` IS NOT NULL;
DECLARE temp_places_ids CURSOR FOR SELECT `id` FROM `places` WHERE `parent_id` = single_unique_parents_id;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN unique_parents_ids;
main_loop_for_parent_ids : LOOP
SET sum_number_of_pois = 0;
IF done = 1 THEN
CLOSE unique_parents_ids;
LEAVE main_loop_for_parent_ids;
END IF;
IF NOT done = 1 THEN
FETCH unique_parents_ids INTO single_unique_parents_id;
OPEN temp_places_ids;
main_loop_for_places : LOOP
IF done = 1 THEN
CLOSE temp_places_ids;
LEAVE main_loop_for_places;
END IF;
IF NOT done = 1 THEN
FETCH temp_places_ids INTO single_place_id;
SELECT COUNT(`id`) INTO temp_number_of_pois FROM `pois` WHERE `place_id` = single_place_id;
SET sum_number_of_pois = sum_number_of_pois + temp_number_of_pois;
END IF;
END LOOP;
UPDATE `places` SET `number_of_pois`=sum_number_of_pois WHERE `id` = single_unique_parents_id;
END IF;
END LOOP;
END$$
DELIMITER ;

Answer 1

I think your problem is about here...
IF NOT done = 1 THEN
FETCH temp_places_ids INTO single_place_id;
SELECT COUNT(`id`) INTO temp_number_of_pois FROM `pois` WHERE `place_id` = single_place_id;
SET sum_number_of_pois = sum_number_of_pois + temp_number_of_pois;
END IF;
The FETCH sets DONE to be 1 when it exhausts the result set, but you proceed because you've already passed the DONE test.
Perhaps...
FETCH temp_places_ids INTO single_place_id;
IF NOT done = 1 THEN
SELECT COUNT(`id`) INTO temp_number_of_pois FROM `pois` WHERE `place_id` = single_place_id;
SET sum_number_of_pois = sum_number_of_pois + temp_number_of_pois;
END IF;