How to check applied patches in the database in Oracle

See which patches were applied inside the database (the datapatch SQL registry), newest first.

-- 12c and later: datapatch SQL registry
SELECT patch_id, patch_type, action, status,
       action_time, description
FROM   dba_registry_sqlpatch
ORDER  BY action_time DESC;

-- 11g (general history on all releases):
-- SELECT action_time, action, namespace, version, comments
-- FROM   dba_registry_history
-- ORDER  BY action_time DESC;