NVL(aa01.NM,'') 은 아무 의미 없는 구문입니다. aa01.NM 과 같습니다.

SELECT pstn_nm
     , pr_action_exec_chps_empno
     , nm
     , pr_objt_grp_nm
     , pr_objtr_nm
     , MIN(DECODE(rn,1,pr_detl1_sn)) pr_detl1_sn_1
     , MIN(DECODE(rn,2,pr_detl1_sn)) pr_detl1_sn_2
     , MIN(DECODE(rn,3,pr_detl1_sn)) pr_detl1_sn_3
     , MIN(DECODE(rn,4,pr_detl1_sn)) pr_detl1_sn_4
     , MIN(DECODE(rn,5,pr_detl1_sn)) pr_detl1_sn_5
     , MIN(DECODE(rn,6,pr_detl1_sn)) pr_detl1_sn_6
     , MIN(DECODE(rn,1,pr_detl2_sn)) pr_detl2_sn_1
     , MIN(DECODE(rn,2,pr_detl2_sn)) pr_detl2_sn_2
     , MIN(DECODE(rn,3,pr_detl2_sn)) pr_detl2_sn_3
     , MIN(DECODE(rn,4,pr_detl2_sn)) pr_detl2_sn_4
     , MIN(DECODE(rn,5,pr_detl2_sn)) pr_detl2_sn_5
     , MIN(DECODE(rn,6,pr_detl2_sn)) pr_detl2_sn_6
  FROM (SELECT c01.pstn_nm
             , b01.pr_action_exec_chps_empno
             , aa01.nm
             , pr_objt_grp_nm
             , pr_objtr_nm
             , DECODE(pr_detl1_sn,'1','직접면담','2','유선통화')    pr_detl1_sn
             , DECODE(pr_detl2_sn,'1','긍정','2','보통','3','부정') pr_detl2_sn
             , ROW_NUMBER() OVER(PARTITION BY c01.pstn_nm
                                            , b01.pr_action_exec_chps_empno
                                            , aa01.nm
                                            , pr_objt_grp_nm
                                            , pr_objtr_nm
                                     ORDER BY pr_detl1_sn
                                            , pr_detl2_sn
                                 ) rn
          FROM tbetcb02      b02
             , mvwtbetkc0801 c01
             , tbetcb01      b01
             , tbetkc07      aa01
             , tbetca01      a01
         WHERE b02.pr_mgmt_pr_ym  = '2008'
           AND b02.pr_kind_cd     = '1'
           AND b02.pr_mgmt_sn     = '4'
           AND b02.pr_objt_blg_cd = '0714000'
           AND b02.pr_objt_grp_cd = '01'
           AND b02.pr_objt_sn     = '249'
           AND b02.pr_objt_blg_cd = c01.pstn_cd
           AND b02.pr_mgmt_pr_ym  = b01.pr_mgmt_pr_ym
           AND b02.pr_kind_cd     = b01.pr_kind_cd
           AND b02.pr_mgmt_sn     = b01.pr_mgmt_sn
           AND b01.pr_action_exec_chps_empno = aa01.emp_no(+)
           AND b02.pr_objt_blg_cd = a01.pr_objt_blg_cd
           AND b02.pr_objt_grp_cd = a01.pr_objt_grp_cd
           AND b02.pr_objt_sn     = a01.pr_objt_sn
        )
 GROUP BY pstn_nm
     , pr_action_exec_chps_empno
     , nm
     , pr_objt_grp_nm
     , pr_objtr_nm