Retrieve posts with a broken thumbnail (thumbnail set to an attachment that does not exist)

brokenthumbnails.sql

SELECT `wp_posts`.`ID`, `wp_posts`.`post_title`, `b`.`ID` as 'thumbnail'
FROM `wp_posts`
INNER JOIN (
	SELECT *
	FROM `wp_postmeta`
	WHERE `meta_key` = '_thumbnail_id'
) AS a ON `wp_posts`.`ID` = `a`.`post_id`
LEFT JOIN (
	SELECT *
	FROM `wp_posts`
) AS b ON `a`.`meta_value` = `b`.`ID`
WHERE true
AND `wp_posts`.`post_type` = 'post'
AND `wp_posts`.`post_status` = 'publish'
AND `b`.`ID` IS NULL
GROUP BY `wp_posts`.`ID`