select 
    LINE_ID as LINE
    ,SEAT_NO AS SEAT_F
    ,SEAT_NO + 2 AS SEAT_T
from
    SEAT_RESERVE AS s
where 
    RSV_STATUS = '0' AND
    EXISTS (
        SELECT 1
        FROM SEAT_RESERVE AS s2
        WHERE s2.LINE_ID = s.LINE_ID
          AND s2.SEAT_NO = s.SEAT_NO + 1
          AND s2.RSV_STATUS = '0'
    ) AND
    EXISTS (
        SELECT 1
        FROM SEAT_RESERVE AS s3
        WHERE s3.LINE_ID = s.LINE_ID
          AND s3.SEAT_NO = s.SEAT_NO + 2
          AND s3.RSV_STATUS = '0'
    )
ORDER BY 
    LINE desc, 
    SEAT_F