oracle数据库查询表空间内存及使用情况

select a.tablespace_name, total, free,(total-free) as usage from

(select tablespace_name, sum(bytes)/1024/1024/1024 as total from dba_data_files group by tablespace_name) a,

(select tablespace_name, sum(bytes)/1024/1024/1024 as free from dba_free_space group by tablespace_name) b

where a.tablespace_name = b.tablespace_name;