Oracle查看所有用户占用的表空间

SELECT OWNER as "用户名", sum(BYTES) / 1024 / 1024 / 1024 as "所有表的大小(GB)"
  FROM DBA_SEGMENTS
 WHERE SEGMENT_NAME in (select t2.OBJECT_NAME
                          from dba_objects t2
                         where t2.OBJECT_TYPE = 'TABLE')
 group by OWNER order by 2 desc