查询object的大小，按照降序排序
select * from user_segments s where s.BYTES is not null order by s.BYTES desc
或
select a.segment_name,
a.segment_type,
a.bytes,
a.bytes / 1024 / 1024 byte_m,
b.created
from dba_segments a
inner join all_objects b
on b.object_type = 'TABLE'
and a.owner = b.owner
and a.segment_name = b.object_name
where a.owner = '用户名'
and a.segment_type = 'TABLE' /* and a.bytes>50000000*/
order by a.bytes desc;
