查询数据库表空间使用情况：

SELECT df.tablespace_name "表空间",
       (df.totalspace - NVL(fs.freespace, 0)) "已使用(MB)",
       NVL(fs.freespace, 0) "剩余(MB)",
       df.totalspace "合计(MB)",
       ROUND(100 * (1 - NVL(fs.freespace, 0) / df.totalspace), 2) "使用率(%)"
  FROM (SELECT tablespace_name, ROUND(SUM(bytes) / 1048576) totalspace
          FROM dba_data_files
         GROUP BY tablespace_name) df,
       (SELECT tablespace_name, ROUND(SUM(bytes) / 1048576) freespace
          FROM dba_free_space
         GROUP BY tablespace_name) fs
 WHERE df.tablespace_name = fs.tablespace_name(+)
 ORDER BY 5 DESC;