How to find top 10 largest sized tables in Oracle

col    owner format a15 col    segment_name format a30 col    segment_type format a15 col    gb format 999,999,999 select  owner ,    segment_name ,    segment_type ,    gb from    (     select    owner     ,    segment_name     ,    segment_type     ,    bytes / 1024 / 1024 / 1024 "gb"     from    dba_segments     where segment_type = 'TABLE'     order    by bytes desc     ) where    rownum < 10