Oracle 查询某个表所占空间

SELECT segment_name AS TABLENAME,

         BYTES B,

           BYTES / 1024 KB,

           BYTES / 1024 / 1024 MB,

            

           BYTES / 1024 / 1024/1024 GB

     FROM user_segments

    where segment_name in ('V30_RPT_VISIT_BAK')

order by bytes desc;