CREATE TABLE BM_CUSTOMER_CONTACT
(
  CUSTOMER_CONTACT_ID  NUMBER                   NOT NULL,
  CUSTOMER_ID          NUMBER                   NOT NULL,
  CONTACT_DICT_ID      NUMBER                   NOT NULL,
  VALUE                VARCHAR2(255 BYTE)       NOT NULL
);

merge into BM_CUSTOMER_CONTACT D
using (select CUSTOMER_ID from BM_CUSTOMER_CONTACT where CONTACT_DICT_ID = 999 and CUSTOMER_ID = :id) S
on (S.CUSTOMER_ID = D.CUSTOMER_ID)
when matched then
  update set D.VALUE = to_char(sysdate, 'yyyy-mm-dd hh24:mi') || ': ' || :msg
when not matched then
  insert (D.CUSTOMER_ID, D.CONTACT_DICT_ID, D.VALUE)
  values (:id, 999, to_char(sysdate, 'yyyy-mm-dd hh24:mi') || ': ' || :msg)

merge into BM_CUSTOMER_CONTACT
using DUAL on (CONTACT_DICT_ID = 999 and CUSTOMER_ID = :id)
when matched then
  update set VALUE = to_char(sysdate, '[yyyy-mm-dd hh24:mi] ') || :msg
when not matched then
  insert (CUSTOMER_ID, CONTACT_DICT_ID, VALUE)
  values (:id, 999, to_char(sysdate, '[yyyy-mm-dd hh24:mi] ') || :msg)