有时候在数据库运维时会发现数据空间不足导致一系列的数据读写问题，因此定期梳理很有必要，以下是从网上找的部分DB管理的SQL，特此记录一下：
SELECT a.tablespace_name "表空间名", a.bytes / 1024 / 1024 "表空间大小(M)", (a.bytes - b.bytes) / 1024 / 1024 "已使用空间(M)", b.bytes / 1024 / 1024 "空闲空间(M)", round(((a.bytes - b.bytes) / a.bytes) * 100, 2) "使用比" FROM (SELECT tablespace_name, sum(bytes) bytes FROM dba_data_files GROUP BY tablespace_name) a, (SELECT tablespace_name, sum(bytes) bytes, max(bytes) largest FROM dba_free_space GROUP BY tablespace_name) b WHERE a.tablespace_name = b.tablespace_name ORDER BY ((a.bytes - b.bytes) / a.bytes) DESC
SELECT file_name, tablespace_name, bytes / 1024 / 1024 "bytes MB", maxbytes / 1024 / 1024 "maxbytes MB" FROM dba_data_files WHERE tablespace_name = 'BI';
Select Segment_Name,Sum(bytes)/1024/1024 From User_Extents Group By Segment_Name
