Best way to calculate maximum of many columns/values per row

Question

Hello,
for a new report with some joined tables I have to calculate the last change date. Since every table has a creation and a (last) modification date, I need to get the maximum value from 8 columns to display it.
Of course I can compare all values by pairs or create a PL/SQL function. But maybe there already exists a fast and easy way to gain this date?
My query so far. Each of the tables has a cr_date and mod_date column:
SELECT
    egvg.baugruppe_nummer || egvg.anlagennummer || egvg.geraetenummer AS systemnummer
    , '=' || egvg.baugruppe_nummer || egvg.anlagennummer || egvg.geraetenummer AS systemnr2
    , egvg.gebrauchsname AS gebrauchsname
    , NVL2(egvr.raumkode, '+' || egvr.raumkode, NULL) AS raumkode
    , egvg.lieferant AS lieferant
    , CASE egvgs.kabelanschluss WHEN 1 THEN 'ja' WHEN 0 THEN 'nein' ELSE NULL END AS kabelanschluss
    , egvges.nennleistung_kva AS nennleistung
    , NULL AS letzte_aenderung
    , CASE WHEN egvg.status_id = -1 THEN 'GERÄT GELÖSCHT' WHEN egvges.status_id = -1 THEN 'EDATEN GELÖSCHT' ELSE NULL END AS status
  FROM
    egv_geraete egvg
    LEFT JOIN egv_geraetestamm egvgs ON egvgs.id = egvg.geraetestamm_id
    LEFT JOIN egv_geraetestamm_edatenstamm egvges ON egvges.geraetestamm_id = egvgs.id
    LEFT JOIN egv_raeume egvr ON egvr.id = egvg.raum_id
    LEFT JOIN egv_edaten_sfp egvsfp ON egvsfp.id = egvges.sfp_idThank you,
Stefan

Answer 1

>
This method works but is there an easier (faster) way to update another table with new data only?
>
Almost anything would be better than that slow-by-slow loop processing.
You don't need a procedure you should just use MERGE for that. See the examples in the MERGE section of the SQL Language doc
http://docs.oracle.com/cd/B28359_01/server.111/b28286/statements_9016.htm
MERGE INTO bonuses D
   USING (SELECT employee_id, salary, department_id FROM employees
   WHERE department_id = 80) S
   ON (D.employee_id = S.employee_id)
   WHEN MATCHED THEN UPDATE SET D.bonus = D.bonus + S.salary*.01
     DELETE WHERE (S.salary > 8000)
   WHEN NOT MATCHED THEN INSERT (D.employee_id, D.bonus)
     VALUES (S.employee_id, S.salary*.01)
     WHERE (S.salary <= 8000);