오라클 구분자로 첫번째, 두번째, 세번째 문자 구하기

SELECT  a.첫번째
              , b.두번째
              , c.세번째
FROM  ( SELECT REGEXP_SUBSTR('031-905-4023', '[^-]*')
                                                            AS 첫번째
        FROM   DUAL                          )  a ,
      ( SELECT REGEXP_SUBSTR(SUBSTR('031-905-4023'
                        , REGEXP_INSTR('031-905-4023','-')+1
              , LENGTH('031-905-4023'))
              , '[^-]*')                                 AS 두번째
        FROM   DUAL                          )  b ,
    ( SELECT REGEXP_SUBSTR('031-905-4023', '[^-]*$')
                                                            AS 세번째
     FROM   DUAL                            )  c
WHERE   1=1    
;