WITH t1 AS
(
    SELECT
        rownum AS rownumm,
        ROW_NUMBER() OVER (partition BY c.maker ORDER BY c.TYPE) rang,
        maker,
        TYPE,
        CASE
            WHEN TYPE LIKE 'PC' THEN 1
            WHEN TYPE LIKE 'Laptop' THEN 2
            WHEN TYPE LIKE 'Printer' THEN 3 ELSE 0
        END AS type_n
    FROM
    (
        SELECT DISTINCT
            maker, TYPE
        FROM Product
        ORDER BY maker
    ) c
)

SELECT
    f.rownumm AS num,
    CASE
        WHEN f.rang = 1 THEN f.maker ELSE ''
    END AS maker,
    s.TYPE
FROM
    t1 f
    LEFT JOIN
    (
        SELECT
            rang,
            maker,
            TYPE,
            type_n,
            CASE WHEN type_n IN (SELECT rang FROM t1 aa WHERE aa.maker = bb.maker AND aa.TYPE_N = bb.RANG) THEN type_n ELSE rang END AS rr
        FROM t1 bb
    ) s ON f.maker = s.maker AND f.rang = s.rr
    ORDER BY rownumm