How to find and delete orphaned product variations from WooCommerce sites.
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'
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'