[쿼리] select해서 insert하는 경우에 select 한 값이 없는 경우... null로 처리되는 경우

INSERT
  INTO SLFTNADEPOLOC
       (
           DEPO_SEQ,
           DEPO_PLC,
           FRST_REG_TS,
           FRST_REGR_ID,
           LAST_MOD_TS,
           LAST_CORT_ID,
           DELETE_YN,
           DEP_CODE
       )
       VALUES
       (
           (
               CASE
                   WHEN
                       (SELECT MAX(NVL(DEPO_SEQ, 0)) +1
                         FROM SLFTNADEPOLOC
                       ) IS NULL
                   THEN 1
                   ELSE
                       (SELECT MAX(NVL(DEPO_SEQ, 0)) +1
                         FROM SLFTNADEPOLOC
                       )
               END
           )
           ,
           'test',
           SYSDATE,
           'test',
           SYSDATE,
           'test',
           'N',
           '46400350000'
       )

========================================================================================

어설프지만 중간에 case문을 사용함으로써 이 문제를 해결했다... -_-

어서 OCP 공부를 하던가 해야지...;;