Oracle第五课（学习笔记）

连接查询

JUL12_CLASS JUL12_STUDENT

SELECT CNAME,SNMAE

FROM JUL12_CLASS C,JUL12_STUDENT S

WHERE C.CID = S.CID;

SELECT CNAME,SNAME

FROM JUL12_CLASS C

JOIN JUL12_STUDENT S ON C.CID= S.CID;

用JOIN 和 ON 连接

左外连接

SELECT CNAME,SNAME

FROM JUL12_CLASS C

LEFT JOIN JUL12_STUDENT S ON C.CID = S.CID;

右外连接

SELECT CNAME，SNAME

FROM JUL12_STUDENT S

RIGHT JOIN JUL12_CLASS C ON C.CID = S.CID;

**************************************************

CREATE TABLE JUL12_S_EMP

AS

SELECT * FROM S_EMP;

SELECT ID ,USERID ,DEPT_ID ,SALARY FROM JUL12_S_EMP;

--找出大于所在部门平均工资的于员工

SELECT ID ,USERID ,DEPT_ID ,SALARY

FROM JUL12_S_EMP A,

(

SELECT DEPT_ID D,AVG(SALARY) S FROM JUL12_S_EMP

GROUP BY DEPT_ID

) D

WHERE A.DEPT_ID = D.D AND A.SALARY > D.S

ORDER BY A.ID ;

SELECT ID ,USERID ,SALARY

FROM JUL12_S_EMP A

WHERE SALARY >

(

SELECT AVG(SALARY)

FROM JUL12_S_EMP B

WHERE A.DEPT_ID = B.DEPT_ID

)

ORDER BY A.ID ;

SELECT ID ,SALARY FROM JUL12_S_EMP A,

(SELECT DEPT_ID, AVG(SALARY) AVGS

FROM JUL12_S_EMP GROUP BY DEPT_ID

==================================================

登录mysql，，，，

转到bin目录下面执行mysql -u root -p password;

没有密码的就这么写：mysql -u root ;

show database;

CREATE DATABASE MYDB;

mysql> use mydb;

mysql> create table student(

id int (4),

name char(10),

age int (4),

address varchar(20)

);

mysql> insert into STUDENT values

(1001,'zhang',23,'jiangsu);

mysql> insert into STUDENT values

(1002,'xiexie',23,'zhejiang');

mysql> insert into STUDENT values

(1003,'aaaa',33,'asdfds');

mysql> insert into STUDENT values

(1004,'sdsd',44,'sdfsdeee');

mysql> insert into STUDENT values

(1005,'sss',32,'wwwssssss');

mysql> insert into STUDENT values

(1006,'zhao',33,'zhonglu');

mysql> insert into STUDENT values

(1007,'xie',33,'kehong');

mysql> insert into STUDENT values

(1008,'good',23,'keqi');

//发现表名 要区分大小写

select * from STUDENT limit 3 －－前三行数据

select * from STUDENT limit 2 OFFSET 3--第四行还是两行数据

SELECT first_name || ' ' || last_name FROM s_emp

where id in (select manager_id from s_emp group by manager_id having count(*) >1);

union联合查询.前后查询内容相加

若有重复则只显示一次,,,若要全部显示则可以使用union all

select 8 from jul12_student where age >12;

union

select * from jul12_student where age <12 and age >10;

intersect此方式为交集 ,即为两个查询的相同的部分进行显示出来

select * from jul12_student where age >12

intersect

select * from jul12_student where age>12 and age <32;

minus此方式也可以当作分页,但是效率最低

此例子的目的在于极少minus的用法,就是用第一个查询出的结果,减去第二个查询出来的结果.如下显示的就是第三个第四条记录.

select * from jul12_student where rownum <=5

minus

select * from jul12_student where rownum <=3;

************************Objectives*************

Add and modify columns;添加和修改列

删除表 drop table [tablename]

DDL 数据定义语言,不可ROOLBACK

----ADD COLUMN

ALTER TABLE JUL12_STUDENT

ADD ABC CHAR(10);

----DELETE COLUMN

ALTER TABLE JUL12_STUDENT

DROP COLUMN ABC;

----MODIFY

ALTER TABLE JUL12_STUDENT MODIFY AGE VARCHAR(10);

对表的约束的修改

alter table jul12_student

add not null (name)

外键的约束

sql> alter table s_emp

add constraint s_emp_manager_id_fk

foreign key (manager_id)

references s_emp(id);

关闭约束

sql> alter table

disable constraint

开启约束

sql>alter table

enable constraint

更改表名

rename tablename to newtablename

删除表内全部记录

sql>truncate table s_item;

于delete的区别就是不可以ROOLBACK

事务完成后输入

commit;执行

总结Oracle数据库

oracle:

openlabe open123

window:

1.启动和关闭oracle相关的服务;

1:oracle startup shutdown

启动和关闭 listener

1:isnrctl

2.

openlabe /open 123

$sqlplus/nolog

$connect/as sysdba;

-=-=-=-=-=-=-=-=-=-=-=-=

oracle中创建用户

create user abc(用户名) identified by efg(新密码);

例:

create user tarena01 identified by tarena01

给用户授权

grant connect ,resource to tarena01两个权限

收回权限

revoke connect from tarena01(管理员权限登录)

删除一个用户

drop user abc

-=-=-=-=-=-=-=-=-=-=-=-=

mysql 2:操作用户

mysql> show databases;(注意databases我为复数)

杀看用户(user表中存放了用户信息)

mysql> use mysql;

mysql> select user from user;

mysql> select password from user where user ='root';

mysql 2:

grant all on mydb.* to 'aa' identified by 'bb';

给用户授权

grant all on mydb.* to 'aaa' identified by 'bbb';

修改密码的条件

1.进入mysql

mysql> use mysql 进入数据库

mysql> select user,password from user; 查看表内数据

mysql> update user set password =password('ef')wehre user = 'aa'; 利用update更新数据 更新password

mysql> select user,password from user;

alter user 'aa' identified by open234;

flush privileges提交

mysql> GRANT USAGE ON *.* TO aa IDENTIFIED BY 'lrock'

二 :sql

1.create table person(

a int(3) primary key,

b varchar(10),

c datetime

);

insert into person values (1,'aa',now());

insert into person values (2,'bb',now());

insert into person values (3,'cc',now());

insert into person values (4,'dd',now());

2:

select insert delete update;

性能分析的依据

oracle: set autotrace on

set timing on

mysql: explain p312 16.3

多表查询:

推荐是哟你连接查询

in(exists)

1:

rownum limit offset

2:

求每个年龄段的人数 group by age/10

３:

删除表里重复的记录

rowid具有唯一性质,标识硬盘数据存储的位置 min max ...

4:

取出表中随机的三条记录

dbms_random.random

5:

取出工资大于本部门平均工资的人.