I think more something like this:

```sql
SELECT GROUP_CONCAT('', previews.caption) FROM previews INNER JOIN translations ON previews.caption = translations.id INNER JOIN addons ON previews.addon_id = addons.id WHERE translations.id IS NOT NULL AND addons.addontype_id = 11 INTO @ids;
UPDATE previews SET caption = NULL, modified = NOW() WHERE FIND_IN_SET(caption, @ids);
DELETE FROM translations WHERE FIND_IN_SET(id, @ids);