WITH RECURSIVE numbers AS (
    SELECT 1 AS n
    UNION ALL
    SELECT n + 1
    FROM numbers
    WHERE n < 13
)
,ALPHABETS AS (
    SELECT 65 AS code
    UNION ALL
    SELECT code + 1
    FROM ALPHABETS
    WHERE code < 69
)
SELECT LINE, SEAT_F, SEAT_T
FROM 
(
SELECT CHAR(ALPHABETS.code) AS LINE, NUMBERS.N AS SEAT_F, NUMBERS.N+2 AS SEAT_T
FROM ALPHABETS
CROSS JOIN NUMBERS
) AS A
WHERE (
 SELECT B.RSV_STATUS
 FROM SEAT_RESERVE AS B
 WHERE LINE_ID = A.LINE
   AND SEAT_NO = A.SEAT_F
) + 
(
 SELECT B.RSV_STATUS
 FROM SEAT_RESERVE AS B
 WHERE LINE_ID = A.LINE
   AND SEAT_NO = A.SEAT_F+1
) + 
(
 SELECT B.RSV_STATUS
 FROM SEAT_RESERVE AS B
 WHERE LINE_ID = A.LINE
   AND SEAT_NO = A.SEAT_F+2
) = 0
ORDER BY LINE DESC,SEAT_F