correct

 SELECT 

    t.owner,

    t.table_name,

    s.tablespace_name,

    ROUND(s.bytes / 1024 / 1024, 2) AS size_mb,

    t.num_rows,

    t.last_analyzed,

    o.last_ddl_time AS last_modified

FROM dba_tables t

JOIN dba_segments s 

    ON t.owner = s.owner 

   AND t.table_name = s.segment_name 

   AND s.segment_type = 'TABLE'

JOIN dba_objects o

    ON t.owner = o.owner 

   AND t.table_name = o.object_name 

   AND o.object_type = 'TABLE'

WHERE t.owner NOT IN (

    'SYS', 'SYSTEM', 'XDB', 'OUTLN', 'MDSYS', 'ORDDATA', 'ORDSYS',

    'CTXSYS', 'DBSNMP', 'APPQOSSYS', 'AUDSYS', 'DVSYS',

    'GSMADMIN_INTERNAL', 'ANONYMOUS', 'WMSYS', 'OLAPSYS',

    'LBACSYS', 'SI_INFORMTN_SCHEMA'

)

AND REGEXP_LIKE(t.table_name, 

    '(\d+$|' ||

    '(JAN|FEB|MAR|APR|MAY|JUN|JUL|AUG|SEP|OCT|NOV|DEC)|' ||

    '(JANUARY|FEBRUARY|MARCH|APRIL|JUNE|JULY|AUGUST|SEPTEMBER|OCTOBER|NOVEMBER|DECEMBER)|' ||

    '(20[0-9]{2}[_]?(0[1-9]|1[0-2]))$|' ||

    '((0[1-9]|1[0-2])(20[0-9]{2}))$)',

    'i'

)

ORDER BY size_mb DESC;