Remove gallery images from out of stock products sql query?

I’d like to remove gallery images only (not featured image) from sold products on my woocommerce site in bulk because my server storage limits are being reached. I have nearly 2000 out of stock products, so doing this manually is not an option. I do not want to delete the products or featured image, only the gallery images.

I couldn’t find a plugin that would do this, so just to get something working quickly I tried to create an sql query that would remove the product ID from wp_posts.post_parent for just the product gallery attachments but my query isn’t working. The idea is if the query can unattach the images, then I can go into the media library and delete all unattached images in bulk which should also delete the physical file from the server.

Here is my attempt, hopefully someone can look at this and see the problem:

UPDATE
wp_posts
inner join
wp_postmeta on find_in_set(wp_posts.ID, wp_postmeta.meta_value)
SET
wp_posts.post_parent = ”
WHERE
wp_postmeta.meta_value = ‘outofstock’
AND
wp_postmeta.meta_value = wp_posts.post_parent
AND
wp_posts.post_type = ‘attachment’
AND
wp_posts.comment_status = ‘open’;

Thanks!