SELECT [LINE]
,[SEAT_F]
,[SEAT_T]
FROM (
SELECT [LINE_ID] AS [LINE]
,CASE WHEN SUM ([RSV_STATUS]) OVER ( ORDER BY [LINE_ID] ROWS 2 PRECEDING ) = 0 THEN [SEAT_NO] - 2
    END AS [SEAT_F]
,CASE WHEN SUM ([RSV_STATUS]) OVER ( ORDER BY [LINE_ID] ROWS 2 PRECEDING ) = 0 THEN [SEAT_NO]
    END AS [SEAT_T]
FROM [SEAT_RESERVE]
) AS [SEAT_RESERVE]
WHERE [SEAT_F] IS NOT NULL
AND [SEAT_T] IS NOT NULL
ORDER BY [LINE] DESC
,[SEAT_F] ASC