第十二天 SQL语句 查询

select查询语句

• 查看hr用户名下的表，解锁hr用户：

$ sqlplus / as sysdba或SQL> conn / as sysdba

SQL> show user

SQL> select table_name from dba_tables where owner='HR';

SQL> select * from hr.employees;

SQL> alter user hr account unlock identified by hr;

$ sqlplus hr/hr或者SQL> conn hr/hr

SQL> show user

SQL> select * from tab;

select * from employees;

SQL> desc employees    查看表结构

 

练习：

查看scott用户名下的表，解锁scott用户：

scott/tiger

 

 

• 使用sqlplus的全屏编辑功能：

$ echo $EDITOR

SQL> select * from hr.employees;

SQL> ed

SQL> / 执行

 

 

 

• 基础select语句：

 

SQL> select * from employees;

SQL> desc employees

 

SQL> select LAST_NAME, SALARY, COMMISSION_PCT from employees;

SQL> desc departments

 

SQL> select department_id, department_name from departments;

SQL> select distinct DEPARTMENT_ID from employees;

SQL> select last_name, salary*12*(1+commission_pct) total_salary, department_id from employees;

 

SQL> select first_name||', '||last_name from employees;       

 

SQL> select first_name||', '||last_name fullname from employees;

 

练习：

输出下列员工信息：

Eleni(first_name) Zlotkey(last_name) employeeid is ... at department .. total salary is …

• 使用连字符构造语句：

SQL> select table_name from user_tables;

SQL> select 'grant select on hr.'||table_name||' to scott;' from user_tables;

 

SQL> spool /home/oracle/grant.sql

SQL> select 'grant select on hr.'||table_name||' to scott;' from user_tables;

SQL> spool off

$ vi /home/oracle/grant.sql     去除没用的行

SQL> @/home/oracle/grant.sql

• 单引号的处理：

SQL> select 'I'm teaher' from dual;

ERROR:

ORA-01756: quoted string not properly terminated

SQL> select 'I''m teaher' from dual;

SQL> select q'{I'm teaher}' from dual; []<>()都可以