SELECT
 SV1.LINE_ID AS LINE,
 SV1.SEAT_NO AS SEAT_F,
 MAX(SV2.SEAT_NO) AS SEAT_T

FROM
 SEAT_RESERVE AS SV1
 INNER JOIN SEAT_RESERVE AS SV2
  ON SV1.LINE_ID = SV2.LINE_ID

WHERE
 SV2.SEAT_NO BETWEEN SV1.SEAT_NO AND SV1.SEAT_NO + (3 - 1)
GROUP BY
 SV1.LINE_ID,
 SV1.SEAT_NO
HAVING
 COUNT(NULLIF(SV2.RSV_STATUS, '1')) = 3
 
ORDER BY
 SV1.LINE_ID DESC,
 SV2.SEAT_NO ASC;