Oracle查询表空间剩余

SELECT t1 表空间,z 总表空间,z-s 已用表空间,s 剩余表空间,ROUND((z-s)/z*100,2) “使用率%”
From （Select tablespace_name t1,Sum(bytes) s
From DBA_FREE_SPACE Group by tablespace_name),
(Select tablespace_name t2,Sum(bytes) z
From DBA_DATA_FILES Group by tablespace_name) Where t1=t2;