How to query the OPatch inventory from SQL in Oracle

Query the OPatch inventory straight from SQL, with no shell access needed, using DBMS_QOPATCH.

-- Readable inventory of patches in the Oracle Home
SELECT xmltransform(dbms_qopatch.get_opatch_lsinventory,
                    dbms_qopatch.get_opatch_xslt) AS lsinventory
FROM   dual;

-- datapatch (SQL patch) status
SELECT dbms_qopatch.get_sqlpatch_status FROM dual;