SELECT A.*
        , (SELECT COUNT(H.rs_hroom_seq) 
            FROM RS_HMST R
            INNER JOIN RS_HROOM H ON R.rs_hmst_seq = H.rs_hmst_seq
            WHERE R.ht_mst_seq = A.ht_mst_seq
            AND H.ht_room_seq = A.ht_room_seq
            AND R.rs_status_cd != 'RSSTAA004'
            ) as rs_cnt
FROM HT_ROOM A
WHERE A.ht_room_seq = :ht_room_seq