Insert and by pass unique constraint

col1 is the unique index

insert into table1 (col1,col2)
SELECT 'VALUE1','VALUE2' FROM dual where 'VALUE1' not in (select col1 from table1 where col1='VALUE1')

update and select in oracle

UPDATE INCOMING_LEAD
SET (INCOMING_LEAD.DEPARTMENT_CD, INCOMING_LEAD.PROGRAM_CD,
    INCOMING_LEAD.EFFORT_CD, INCOMING_LEAD.OFFER_CD) =
   (SELECT OFFER_INPUT_KEYCODE.DEPARTMENT_CD,
       OFFER_INPUT_KEYCODE.PROGRAM_CD, OFFER_INPUT_KEYCODE.EFFORT_CD,
       OFFER_INPUT_KEYCODE.OFFER_CD
    FROM OFFER_INPUT_KEYCODE
    WHERE OFFER_INPUT_KEYCODE.INPUT_KEYCODE =
          INCOMING_LEAD.PROMO_INITIAL_KEYCODE)