Top 30 segments grouped by segment type

SET LINESIZE 155
SET PAGESIZE 9999
SET VERIFY   OFF

BREAK ON segment_type SKIP 1
COMPUTE SUM OF bytes ON segment_type

COLUMN segment_type        FORMAT A20                HEADING 'Segment Type'
COLUMN owner               FORMAT A15                HEADING 'Owner'
COLUMN segment_name        FORMAT A30                HEADING 'Segment Name'
COLUMN partition_name      FORMAT A30                HEADING 'Partition Name'
COLUMN tablespace_name     FORMAT A20                HEADING 'Tablespace Name'
COLUMN bytes               FORMAT 9,999,999,999,999  HEADING 'Size (in bytes)'
COLUMN extents             FORMAT 999,999,999        HEADING 'Extents'

SELECT
    a.segment_type      segment_type
  , a.owner             owner
  , a.segment_name      segment_name
  , a.partition_name    partition_name
  , a.tablespace_name   tablespace_name
  , a.bytes             bytes
  , a.extents           extents
FROM
    (select
         b.segment_type
       , b.owner
       , b.segment_name
       , b.partition_name
       , b.tablespace_name
       , b.bytes
       , b.extents
     from
         dba_segments b
     order by
         b.bytes desc
    ) a
WHERE
    rownum < 31
ORDER BY
    segment_type, bytes desc, owner, segment_name
/