With문 쓰면 빠른가요?

가상테이블을 메모리에서 만들고 접근해서 빠르다는데 무슨말인지;; 조회한다음에는 삭제되고..

토드에서 실행계획도 뽑아봤는데 XML로.. 도통 뭐가 모르겠다는;;  전부 Full Scan 하고 있는건 보이는데..

Index도 걸긴걸었고.. 조금만 도와주세요.. 쿼리 한번 올려보겠습니다.

   SELECT X.*
    FROM (
    SELECT ROWNUM AS NUM, Y.*
    FROM (
    SELECT
    A.INQ_HIST_NO ,
    B.INST_CD ,
    SUBSTR(I.DESC_V, 0,1) || SUBSTR(G.DESC_V, 0,1) AS SCHL_GRADE ,
    D.NAME_V AS PISU_INST_NM ,
    A.RG_INST_CD ,
    C.NAME_V AS RG_INST_NM ,
    A.RG_ID ,
    E.NAME_V AS RG_ID_NM ,
    B.INQ_CD ,
    F.CD_NM AS INQ_NM ,
    CASE WHEN A.NAME IS NOT NULL AND A.BMD IS NOT NULL THEN H.NAME_V || ' <![CDATA[<br />]]> ' || A.NAME || ' ( ' || A.BMD || ' ) '
WHEN A.NAME IS NOT NULL AND A.BMD IS NULL THEN H.NAME_V || ' <![CDATA[<br />]]> ' || A.NAME
WHEN A.NAME IS NULL AND A.BMD IS NOT NULL THEN H.NAME_V || ' <![CDATA[<br />]]> ' || A.BMD
WHEN A.NAME IS NULL AND A.BMD IS NULL THEN H.NAME_V
END AS SRCH_CNDTN ,
    CASE WHEN A.NAME IS NOT NULL AND A.BMD IS NOT NULL THEN H.NAME_V || ' , ' || A.NAME || ' ( ' || A.BMD || ' ) '
WHEN A.NAME IS NOT NULL AND A.BMD IS NULL THEN H.NAME_V || ' , ' || A.NAME
WHEN A.NAME IS NULL AND A.BMD IS NOT NULL THEN H.NAME_V || ' , ' || A.BMD
WHEN A.NAME IS NULL AND A.BMD IS NULL THEN H.NAME_V
END AS SRCH_CNDTN_XLS ,
    SUBSTR(A.RG_DTM, 0, 8) AS RG_DTM
    FROM TBL_INQ_HIST A
    JOIN TBL_ORGANIZATION C ON A.RG_INST_CD = C.ORG_CD_V
    JOIN TBL_ORGANIZATION D ON C.TORG_CD_V = D.ORG_CD_V
    JOIN TBL_MEMBER E ON A.RG_ID = E.MEMBER_ID_V AND A.RG_INST_CD = E.MEMBER_CD_V
    JOIN TBL_CODE G ON C.GRADE_N = G.CODE_N
    JOIN TBL_ORGANIZATION H ON A.SCHL = H.ORG_CD_V
    LEFT OUTER JOIN (SELECT INQ_HIST_NO ,
    MAX(INST_CD) AS INST_CD ,
    MAX(INQ_CD) AS INQ_CD ,
    MAX(GRDTN_DT) AS GRDTN_DT
    FROM TBL_INQ_HIST_DTS
    GROUP BY INQ_HIST_NO )B
    ON A.INQ_HIST_NO = B.INQ_HIST_NO
    LEFT OUTER JOIN TBL_COM_CD F ON B.INQ_CD = F.CD AND F.UPR_CD = 'HST004'
    LEFT OUTER JOIN TBL_CODE I ON C.EST_N = I.CODE_N
    ORDER BY A.INQ_HIST_NO DESC ) Y
    WHERE ROWNUM <=10 ) X
    WHERE NUM >=1