SELECT
    LINE_ID AS LINE,
    SEAT_NO AS SEAT_F,
    SEAT_NO + 2 AS SEAT_T
FROM SEAT_RESERVE
WHERE RSV_STATUS = 0  -- 空いている席のみ
AND NOT EXISTS (
    SELECT 1
    FROM SEAT_RESERVE AS SR2
    WHERE SEAT_NO%5
        AND SR2.RSV_STATUS <> 0
)
ORDER BY LINE_ID, SEAT_NO;