Select a.tablespace_name "表空间名", 
total "表空间大小", 
free "表空间剩余大小", 
(total - free) "表空间使用大小", 
total / (1024 * 1024 * 1024) "表空间大小(G)", 
free / (1024 * 1024 * 1024) "表空间剩余大小(G)", 
(total - free) / (1024 * 1024 * 1024) "表空间使用大小(G)", 
round((total - free) / total, 4) * 100 "使用率 %" 
FROM (Select tablespace_name, SUM(bytes) free 
FROM dba_free_space 
GROUP BY tablespace_name) a, 
(Select tablespace_name, SUM(bytes) total 
FROM dba_data_files 
GROUP BY tablespace_name) b 
Where a.tablespace_name = b.tablespace_name