select 
b.file_id 文件ID号,b.tablespace_name 表空间名,b.bytes/1024/1024||'M'字节数,(b.bytes-sum(nvl(a.bytes,0)))/1024/1024||'M' 已使用,sum(nvl(a.bytes,0))/1024/1024||'M' 剩余空间,100 - sum(nvl(a.bytes,0))/(b.bytes)*100 占用百分比 
from dba_free_space a,dba_data_files b 
where a.file_id=b.file_id 
group by b.tablespace_name,b.file_id,b.bytes 
order by b.file_id; 
查询结果如下：

0、查看用户表、索引、分区表占用空间
select segment_name,sum(bytes)/1024/1024 Mbytese from user_segments group by segment_name;
1、表占用空间：select segment_name,sum(bytes)/1024/1024 Mbytese from user_segments where segment_type='TABLE' group by segment_name;
2、索引占用空间：select segment_name,sum(bytes)/1024/1024 from user_segments where segment_type ='INDEX' group by segment_name;
3、分区表TABLE PARTITION占用空间：select segment_name,sum(bytes)/1024/1024 Mbytes from user_segments where segment_type='TABLE PARTITION' group by segment_name;