Select or Delete WooCommerce Orphaned Variations

delete.txt

DELETE o FROM `wp_posts` o
LEFT OUTER JOIN `wp_posts` r
ON o.post_parent = r.ID
WHERE r.id IS null AND o.post_type = 'product_variation'

select.txt

SELECT * FROM `wp_posts` o
LEFT OUTER JOIN `wp_posts` r
ON o.post_parent = r.ID
WHERE r.id IS null AND o.post_type = 'product_variation'

why is r.ID uppercase on line 3 then lowercase on line 4? does this matter?

cheers