select
  a.*,                                     -- NUM_BACKUPSETS NUMBER
  case                                     -- OLDEST_BACKUP_TIME DATE 
     when original_input_bytes/decode(output_bytes, 0, null, output_bytes) > 1 
     then original_input_bytes/decode(output_bytes, 0, null, output_bytes) 
     else 1 end compression_ratio,
  sys.dbms_rcvman.num2displaysize(original_input_bytes) original_input_bytes_display,-- NEWEST_BACKUP_TIME DATE
  sys.dbms_rcvman.num2displaysize(output_bytes) output_bytes_display,-- OUTPUT_BYTES NUMBER
  sys.dbms_rcvman.num2displaysize(original_inprate_bytes) original_inprate_bytes_display,-- ORIGINAL_INPUT_BYTES NUMBER
  sys.dbms_rcvman.num2displaysize(output_rate_bytes) output_rate_bytes_display -- ORIGINAL_INPRATE_BYTES NUMBER
  -- missed columns from describe:
  ---- OUTPUT_RATE_BYTES NUMBER
  ---- COMPRESSION_RATIO NUMBER
  ---- ORIGINAL_INPUT_BYTES_DISPLAY VARCHAR2(4000)
  ---- OUTPUT_BYTES_DISPLAY VARCHAR2(4000)
  ---- ORIGINAL_INPRATE_BYTES_DISPLAY VARCHAR2(4000)
  ---- OUTPUT_RATE_BYTES_DISPLAY VARCHAR2(4000)
from
  (
  select
    count(*) num_backupsets,
    min(start_time) oldest_backup_time,
    max(start_time) newest_backup_time,
    sum(output_bytes) output_bytes,
    sum(original_input_bytes) original_input_bytes,
    avg(original_inprate_bytes) original_inprate_bytes,
    avg(output_rate_bytes) output_rate_bytes
  from
    (
    select
      unique set_stamp,
      set_count,
      start_time,
      output_bytes,
      original_input_bytes,
      original_inprate_bytes,
      output_rate_bytes,
      compression_ratio
    from
      v$backup_set_details))a