SQL基础

1.  connect  sys/toor as sysdba      

2. show user

3. select username from dba_users

4. alter user scott account unlock;   or  alter user scott account lock;   

5. connect scott/tiger

6.desc dba_tablespaces   //需要管理员账号，才可以使用的命令

7.select  tablespace_name from dba_tablespaces;

8.alter user system default system;

9.