数据库表空间使用率查询

select a.a1 表空间名称,
       c.c2 类型,
       c.c3 区管理,
       b.b2 / 1024 / 1024 表空间大小M,
       (b.b2 - a.a2) / 1024 / 1024 已使用M,
       substr((b.b2 - a.a2) / b.b2 * 100, 1, 5) 利用率
  from (select tablespace_name a1, sum(nvl(bytes, 0)) a2
          from dba_free_space
         group by tablespace_name) a,
       (select tablespace_name b1, sum(bytes) b2
          from dba_data_files
         group by tablespace_name) b,
       (select tablespace_name c1, contents c2, extent_management c3
          from dba_tablespaces) c
 where a.a1 = b.b1
   and c.c1 = b.b1;