DDL

CREATE OR REPLACE TRIGGER trg_UID_tab1
AFTER INSERT OR UPDATE
ON tab1
FOR EACH row
/* This is a sample of an INSERT/UPDATE
   trigger which populates column F1 in table TAB1 
   on INSERT and reset column F2 on update */
DECLARE
  lv_next_val NUMBER;
BEGIN
  IF updating THEN
     IF :old.f2=pkg1.gc_magic_date THEN
        :NEW.f2 := TRUNC(SYSDATE);
     END IF;
   ELSIF inserting THEN
     lv_next_val := pkg1.fcn_seq1_get_next;
     :NEW.f1 := lv_next_val;
     :NEW.f2 := TRUNC(SYSDATE);
  END IF;
END;
/