MYSQL GROUP_CONCAT and IN - mysql

Question

I have a little query, it goes like this:
It's slightly more complex than it looks, the only issue is using the output of one subquery as the parameter for an IN clause to generate another. It works to some degree - but it only provides the results from the first id in the "IN" clause. Oddly, if I manually insert the record ids "00003,00004,00005" it does give the proper results.
What I am seeking to do is get second level many to many relationship - basically tour_stops have items, which in turn have images. I am trying to get all the images from all the items to be in a JSON string as 'item_images'. As stated, it runs quickly, but only returns the images from the first related item.
SELECT DISTINCT
tour_stops.record_id,
(SELECT
GROUP_CONCAT( item.record_id ) AS in_item_ids
FROM tour_stop_item
LEFT OUTER JOIN item
ON item.record_id = tour_stop_item.item_id
WHERE tour_stop_item.tour_stops_id = tour_stops.record_id
GROUP BY tour_stops.record_id
) AS rel_items,
(SELECT
CONCAT('[ ',
GROUP_CONCAT(
CONCAT('{ \"record_id\" : \"',record_id,'\",
\"photo_credit\" : \"',photo_credit,'\" }')
)
,' ]')
FROM images
WHERE
images.attached_to IN(rel_items) AND
images.attached_table = 'item'
ORDER BY img_order ASC) AS item_images
FROM tour_stops
WHERE
tour_stops.attached_to_tour = $record_id
ORDER BY tour_stops.stop_order ASC
Both of these below answers I tried, but it did not help. The second example (placing the entire first subquery inside he "IN" statement) not only produced the same results I am already getting, but also increased query time exponentially.
EDIT: I replaced my IN statement with
IN(SELECT item_id FROM tour_stop_item WHERE tour_stops_id = tour_stops.record_id)
and it works, but it brutally slow now. Assuming I have everything indexed correctly, is this the best way to do it?
using group_concat in PHPMYADMIN will show the result as [BLOB - 3B]
GROUP_CONCAT in IN Subquery
Any insights are appreciated. Thanks

Answer 1

I am surprised that you can use rel_items in the subquery.
You might try:
concat(',', images.attached_to, ',') like concat('%,', rel_items, ',%') and
This may or may not be faster. The original version was fast presumably because there are no matches.
Or, you can try to change your in clause. Sometimes, these are poorly optimized:
exists (select 1
from tour_stop_item
where tour_stops_id = tour_stops.record_id and images.attached_to = item_id
)
And then be sure you have an index on tour_stop_item(tour_stops_id, item_id).