SELECT 
    t1.LINE_ID,
    t1.SEAT_NO AS START_SEAT_NO,
    t3.SEAT_NO AS END_SEAT_NO
FROM 
    SEAT_RESERVE as t1
JOIN 
    SEAT_RESERVE as t2 ON t1.LINE_ID = t2.LINE_ID AND t2.SEAT_NO = t1.SEAT_NO + 1
JOIN 
    SEAT_RESERVE as t3 ON t1.LINE_ID = t3.LINE_ID AND t3.SEAT_NO = t1.SEAT_NO + 2
WHERE 
    t1.RSV_STATUS = 0 AND
    t2.RSV_STATUS = 0 AND
    t3.RSV_STATUS = 0
ORDER BY 
    t1.LINE_ID, t1.SEAT_NO;