查询预定义表空间：
SQL> select TABLESPACE_NAME,CONTENTS from dba_tablespaces;
SQL> select FILE_NAME, TABLESPACE_NAME from dba_data_files;
SYSTEM 系统表
SYSAUX 系统辅助表，不断变化
UNDOTBS1 撤销表空间，放撤销数据——修改之前的旧数据，是系统自动维护的（oracle 独有）
TEMP 临时表空间
USERS
EXAMPLE
数据字典/动态性能视图
SQL> conn hr/hr
SQL> desc user_tables
SQL> select TABLE_NAME from user_tables;
SQL> desc user_views
SQL> select VIEW_NAME from user_views;
SQL> desc user_indexes
SQL> select INDEX_NAME, TABLE_NAME from user_indexes;
SQL> conn scott/tiger
SQL> select TABLE_NAME from user_tables; user_表示用户自己的
SQL> select VIEW_NAME from user_views;
SQL> select INDEX_NAME, TABLE_NAME from user_indexes;
SQL> conn hr/hr
SQL> select count(*) from all_tables; all_表示的是有权限访问的对象
SQL> conn scott/tiger
SQL> select count(*) from all_tables;
SQL> conn hr/hr
SQL> select count(*) from dba_tables;
SQL> conn scott/tiger
SQL> select count(*) from dba_tables;
SQL> desc v$instance
SQL> desc v$database
Dml语句只能删除简单视图，无链接，运算等
以v$ 开头的动态性能视图
存储管理
查询预定义表空间：
SQL> select TABLESPACE_NAME,CONTENTS from dba_tablespaces;
SQL> select FILE_NAME, TABLESPACE_NAME from dba_data_files;
SYSTEM 系统表
SYSAUX 系统辅助表，不断变化
UNDOTBS1 撤销表空间，放撤销数据——修改之前的旧数据，是系统自动维护的（oracle 独有）
TEMP 临时表空间
USERS
EXAMPLE
创建新表空间：
SQL> create tablespace tbs01 datafile '/u01/app/oracle/oradata/orcl/tbs01.dbf' SIZE 10M AUTOEXTEND ON NEXT 10M MAXSIZE 100M;
在指定的表空间中创建表：
SQL> create table t1 tablespace tbs01 as select * from dba_objects where 1=0;
SQL> select bytes, blocks, extents, tablespace_name from dba_segments where segment_name='T1';
SQL> insert into t1 select * from dba_objects;
SQL> select bytes, blocks, extents, tablespace_name from dba_segments where segment_name='T1';
SQL> select extent_id, bytes, blocks from dba_extents where segment_name='T1';
SQL> insert into t1 select * from t1;
SQL> insert into t1 select * from t1;
SQL> insert into t1 select * from t1;
SQL> select bytes, blocks, extents, tablespace_name from dba_segments where segment_name='T1';
SQL> select extent_id, bytes, blocks from dba_extents where segment_name='T1';
SQL> insert into t1 select * from t1; 空间不足，报错
SQL> rollback;
SQL> select bytes, blocks, extents, tablespace_name from dba_segments where segment_name='T1'; 空间不释放
SQL> alter table t1 move; 释放空间
只读表空间：
SQL> alter tablespace tbs01 read only;
SQL> delete t1; 禁止dml
SQL> insert into t1 select * from t1; 禁止dml
SQL> create table t2 (x int) tablespace tbs01; 失败
SQL> alter table t1 add (x int); 成功
SQL> update t1 set x=1; 失败
SQL> drop table t1; 成功
dml和ddl的区别
改变表空间大小：
resize，autoextend，add datafile
删除表空间：
SQL> drop tablespace tbs01 including contents and datafile;