select owner,segment_name,segment_type,sum(bytes)/1024/1024 from dba_segments where tablespace_name=upper('&tbs_name')  group by owner,segment_name,segment_type;

感谢您的回复！

在dba_tables或者dba_indexes这两个视图中，有个sample_size参数，
sample_size是否能准确表示表或者索引的大小呢？

col segment_name for a30
col type for a10
col size_MB for 999,999,999.99
compute sum of   size_MB  on owner 
break on owner 

select OWNER,regexp_substr(SEGMENT_type,'[^ ]+') type,SEGMENT_NAME,SUM(BYTES)/1024/1024 size_MB 
from dba_segments 
where tablespace_name='USERS'    ---need modify
AND (SEGMENT_TYPE LIKE 'TABLE%' OR SEGMENT_TYPE LIKE 'INDEX%' )
AND segment_name not like 'BIN$%'
group by owner,regexp_substr(SEGMENT_type,'[^ ]+'),SEGMENT_NAME
order by 1,2 DESC;