7月27

Ddl语句，数据定义表 ，创建删除。SQL  结构化查询语句   DML数据操控表：对数据进行操作，如增删查改

Grid control网络控制 control 像是一个集成的管理工具。Bi做数据仓库的应用。

Entity实体集    每个实体集是表，每个关系是表

数据流程：建模----把用户脑海里的变成er模型表述----关系数据库中的表table model物理化-----在磁盘上进行配置。

1. 查看hr用户名下的表，解锁hr用户：

$ sqlplus / as sysdba（直接利用操作系统身份验证）或SQL> conn / as sysdba在sql里切换身份

SQL> show user  进行身份确认

SQL> select table_name from dba_tables where owner='HR';      查看里面有多少表

SQL> select * from hr.employees;

SQL> alter user hr account unlock identified by hr;    进行解锁并分配口令

$ sqlplus hr/hr或者SQL> conn hr/hr

SQL> show user

SQL> select * from tab;  

SQL> select * from employees;          自己名下的表就不用写前缀

SQL> desc employees       查看表结构

 

1. 使用sqlplus的全屏编辑功能：

$ echo $EDITOR

SQL> select * from hr.employees;

SQL> ed

SQL> / 执行

 

查询永远是行列的交叉。

Select last_name,salary    确定列

From employees   来自哪张表

Where department_id=90   确定行

Sql没有大小写之分，但一般语法关键字大写，对象的名称小写

 

可以对查询的结果，进行额外的运算

ANNUAL 列的别名，后加列名，可以写as 也可以不写

例：select last_name, salary*12*(1+COMMISSION_PCT) annual_salary from employees;

 

链接操作符|| ，为了让输出的信息可读性更高，还可拼凑select语句

Grant select on hr.employees to user01;把用户名下的表权限给user01

单引号是字符串的定界符。

Distinct去除重复值

Desc快速了解表结构

Where语句进行行和列的查询

字符串必须用单引号引起来     oracle的字符串区分大小写     日期：格式敏感

Select sysdate from dual;  dual 空表，保存语法的完整性

Select last-name fyrom employees where hire_date=to_date(‘2006-05-23’, ‘yyyy-mm-dd’)

To_date 进行格式转换

1. 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 …

1. 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

1. 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

where和order by

数字条件：

SQL> select salary from employees where employee_id=100;

字符串大小写敏感：

SQL> select last_name, salary from employees where last_name='King';

SQL> select last_name, salary from employees where lower(last_name)='king';

SQL> select table_name, tablespace_name from user_tables where table_name='EMPLOYEES';

日期是格式敏感：

SQL> select  sysdate from dual；

SQL> alter session set nls_date_format='RR-Mon-dd';

SQL> select  sysdate from dual；

SQL> select last_name from employees where hire_date='2006-05-23';报错

SQL> select last_name from employees where hire_date='23-MAY-06';

SQL> select last_name from employees where hire_date=to_date('2006-05-23', 'yyyy-mm-dd');

区间查询：

SQL> select last_name from employees where salary>=3400 and salary<=4000;

SQL> select last_name from employees where salary between 3400 and 4000;

SQL> select last_name from employees where salary between 3000 and 5000 and department_id=50;

in：

SQL> select last_name from employees where department_id=30 or department_id=40 or department_id=50;

SQL> select last_name from employees where department_id in (30, 40, 50);

通配符：

SQL> select last_name, job_id from employees where job_id like '%\_MAN' escape '\';

null作为条件：

SQL> select last_name from employees where commission_pct is null;

SQL> select last_name from employees where commission_pct is not null;

and/or/not：

SQL> select last_name, job_id, department_id, salary from employees where job_id='SA_REP' or department_id=50 and salary>=8000;

SQL> select last_name, job_id, department_id, salary from employees where (job_id='SA_REP' or department_id=50) and salary>=8000;