查询oracle数据库里的表空间利用率

select a.tablespace_name, round(a.total_size) "total_size(MB)",
round(a.total_size)-round(b.free_size,3) "used_size(MB)",
round(b.free_size,3) "free_size(MB)", round(b.free_size/total_size*100,2)||'%' free_rate
from ( select tablespace_name, sum(bytes)/1024/1024 total_size
       from dba_data_files
       group by tablespace_name ) a,
       ( select tablespace_name, sum(bytes)/1024/1024 free_size
         from dba_free_space
         group by tablespace_name ) b
       where a.tablespace_name = b.tablespace_name(+);