merge into BM_CUSTOMER_CONTACT CC
using (select 999 as CONTACT_DICT_ID, nvl2(:reason, '['||to_char(sysdate, 'YYYY-MM-DD @ HH24:MI')||'] '||:reason,'***') as VALUE from DUAL) RS
on (CC.CUSTOMER_ID = 99092 and CC.CONTACT_DICT_ID = RS.CONTACT_DICT_ID)
when matched then
  update set CC.VALUE = RS.VALUE
  delete where CC.VALUE = '***'
when not matched then
  insert (CC.CUSTOMER_ID, CC.CONTACT_DICT_ID, CC.VALUE)
  values (99092,        RS.CONTACT_DICT_ID, RS.VALUE)

merge into BM_CUSTOMER_CONTACT CC
using (select 999 as CONTACT_DICT_ID, nvl2(:reason, '['||to_char(sysdate, 'YYYY-MM-DD @ HH24:MI')||'] '||:reason,'***') as VALUE from DUAL) RS
on (CC.CUSTOMER_ID = 99092 and CC.CONTACT_DICT_ID = RS.CONTACT_DICT_ID)
when matched then
  update set CC.VALUE = RS.VALUE
  delete where CC.VALUE = '***'
when not matched then
  insert (CC.CUSTOMER_ID, CC.CONTACT_DICT_ID, CC.VALUE)
  values (99092,        RS.CONTACT_DICT_ID, RS.VALUE)
  where :reason is not null