第一节课：
启动数据库并且使用特定用户连接:
su - oracle;
启动sqlplus并且使用sys连接：
conn / as sysdba;
启动数据库：
startup;
解锁用户：
alter user hr identified by hr;
alter user hr account unlock;
使用hr连接：
conn hr/hr;
select * from tab;
desc employees;
select * from departments;
开发工具：
plsql developer;
toad
特殊字符：
SELECT department_name || q'[ Department's Manager Id: ]' || manager_id
AS "Department and Manager"
FROM departments;
在sqlplus中调用vi：
cd $ORACLE_HOME/sqlplus/admin
vi glogin.sql--加入一行：
define _editor='vi'