     perforations.liner_to              ,
     perforations.liner_perforation_from,
     perforations.liner_perforation_to  ,
-    perforations.who_created, perforations.when_created, perforations.who_updated, perforations.when_updated
+    perforations.who_created,
+    perforations.when_created,
+    coalesce(perforations.who_updated, perforations.who_created),
+    coalesce(perforations.when_updated, perforations.when_created)
   FROM wells.wells_perforations perforations
   INNER JOIN xform_well xform ON perforations.well_id=xform.well_id
   WHERE NOT (liner_from is  null

            WHEN 'Y' THEN TRUE
            WHEN 'N' THEN FALSE
        END                               ,
        casings.when_created, casings.when_updated, casings.who_created, casings.who_updated
    FROM wells.wells_casings casings
    INNER JOIN xform_well xform ON xform.well_id=casings.well_id;


    END AS screen_assembly_type_code,
    screens.screen_slot_size        ,
    screens.when_created            ,
    coalesce(screens.when_updated, screens.when_created),
    screens.who_created             ,
    coalesce(screens.who_updated, screens.who_created)
  FROM wells.wells_screens screens
  INNER JOIN xform_well xform ON xform.well_id=screens.well_id;

