Oracle 查询表大小以及表空间使用率

查看表物理文件大小：select segment_name,bytes/1024/1024 from user_segments/dba_segments;
查看表空间使用情况的SQL语句：
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,
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