oracle查看表占用磁盘空间

SELECT T.OWNER, T.SEGMENT_NAME, SUM(T.BYTES) / 1024 / 1024 M
  FROM DBA_SEGMENTS T
 WHERE T.OWNER = 'user_name'
   AND T.SEGMENT_NAME = 'table_name'
 GROUP BY T.OWNER, T.SEGMENT_NAME;

或者

select sum(bytes/1024/1024) M from user_segments where segment_name='table_name';