上面是用户自己执行时的，如果想看别人的，执行如下:
SELECT t.bytes
  FROM DBA_Segments T,
       (SELECT object_name
          FROM DBA_OBJECTS S
         WHERE TRUNC(S.CREATED) = TRUNC(SYSDATE)
           AND OBJECT_TYPE = 'TABLE'
           and owner='USER1') V
WHERE t.segment_name=v.object_name
      and owner='USER1';