SELECT a.tablespace_name "表空间名",
       total "表空间大小",
       free "表空间剩余大小",
       (total - free) "表占用空间大小",
       ROUND((total - free) / total * 100, 2) || '%' "已使用空间百分比"
  FROM (SELECT tablespace_name, SUM(bytes) / 1024 / 1024 total
          FROM dba_data_files
         GROUP BY tablespace_name) a,
       (SELECT tablespace_name, SUM(bytes) / 1024 / 1024 free
          FROM dba_free_space
         GROUP BY tablespace_name) b
 WHERE a.tablespace_name = b.tablespace_name
 ORDER BY (total - free) DESC;