Delete orphan postmeta and attachment in WordPress database

delete-orphan.sql

-- Delete orphan postmeta
DELETE pm
FROM wp_postmeta pm
LEFT JOIN wp_posts p ON pm.post_id = p.ID
WHERE p.ID IS NULL
;

-- Delete orphan attachment
DELETE p1
FROM wp_posts p1
LEFT JOIN wp_posts p2 ON p1.post_parent = p2.ID
WHERE p1.post_parent > 0 AND p1.post_type = 'attachment' AND p2.ID IS NULL
;