Ubuntu 12.04 安装 MySQL--及简单的Show,Use,Create,drop,alter,CRUD,export,import

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Ubuntu 12.04 安装 MySQL

视频地址: 点击打开链接 http://v.youku.com/v_show/id_XNDU5MDU5Nzky.html

安装: jiangge@ubuntu:~$ sudo apt-get install mysql-server

设置MySQL root的密码

输入用户名和密码: jiangge@ubuntu:~$ mysql -uroot -p

mysql> SHOW DATABASES;+--------------------+| Database           |+--------------------+| information_schema |     | mysql                       | performance_schema || test               |       +--------------------+4 rows in set (0.00 sec)

创建数据库:

mysql> CREATE DATABASE forum;Query OK, 1 row affected (0.03 sec)

mysql> SHOW DATABASES;+--------------------+| Database           |+--------------------+| information_schema    mysql|            || forum              |            | performance_schema || test               |+--------------------+

选中数据库:

mysql> USE forum;Database changed

创建表:

mysql> CREATE TABLE users(    -> id int NOT NULL AUTO_INCREMENT,    -> username varchar(20) NOT NULL,    -> PRIMARY KEY(id)    -> );Query OK, 0 rows affected (0.39 sec)

查看表结构:

mysql> DESC users;+----------+-------------+------+-----+---------+----------------+| Field    | Type        | Null | Key | Default | Extra          |+----------+-------------+------+-----+---------+----------------+| id       | int(11)     | NO   | PRI | NULL    | auto_increment || username | varchar(20) | NO   |     | NULL    |                |+----------+-------------+------+-----+---------+----------------+2 rows in set (0.00 sec)

创建表:

mysql> CREATE TABLE comments(    -> id int NOT NULL AUTO_INCREMENT,    -> body text,    -> PRIMARY KEY(id)    -> );Query OK, 0 rows affected (0.53 sec)

查看表结构:

mysql> DESC comments;+-------+---------+------+-----+---------+----------------+| Field | Type    | Null | Key | Default | Extra          |+-------+---------+------+-----+---------+----------------+| id    | int(11) | NO   | PRI | NULL    | auto_increment || body  | text    | YES  |     | NULL    |                |+-------+---------+------+-----+---------+----------------+2 rows in set (0.00 sec)

增加:

mysql> ALTER TABLE comments ADD created_at datetime;Query OK, 0 rows affected (0.71 sec)Records: 0  Duplicates: 0  Warnings: 0

查看:

mysql> DESC comments;+------------+----------+------+-----+---------+----------------+| Field      | Type     | Null | Key | Default | Extra          |+------------+----------+------+-----+---------+----------------+| id         | int(11)  | NO   | PRI | NULL    | auto_increment || body       | text     | YES  |     | NULL    |                || created_at | datetime | YES  |     | NULL    |                |+------------+----------+------+-----+---------+----------------+3 rows in set (0.00 sec)

删除:

mysql> ALTER TABLE comments DROP created_at;Query OK, 0 rows affected (0.75 sec)Records: 0  Duplicates: 0  Warnings: 0

查看

mysql> DESC comments;+-------+---------+------+-----+---------+----------------+| Field | Type    | Null | Key | Default | Extra          |+-------+---------+------+-----+---------+----------------+| id    | int(11) | NO   | PRI | NULL    | auto_increment || body  | text    | YES  |     | NULL    |                |+-------+---------+------+-----+---------+----------------+2 rows in set (0.00 sec)

安装图形化界面phpmyadmin:

jiangge@ubuntu:~$ sudo apt-get install phpmyadmin

会报错:

The following packages have unmet dependencies:
phpmyadmin : Depends: php5-mysql but it is not going to be installed or
php5-mysqli but it is not installable
Recommends: php5-gd but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

解决方法:

apt-get -f install

sudo apt-get install apache2 php5-mysql libapache2-mod-php5

又报错:

The following packages have unmet dependencies:
php5-mysql : Depends: php5-common (= 5.3.10-1ubuntu3) but 5.3.10-1ubuntu3.4 is to be installed
E: Unable to correct problems, you have held broken package

继续解决:

jiangge@ubuntu:~$ sudo apt-get install php5-common

啊啊啊啊啊啊啊啊啊啊啊啊啊啊啊啊啊啊啊啊啊没有解决掉啊.............

http://happycasts.net/episodes/39?autoplay=true 8分30秒..

TODO ......

=======================以下笔记根据网上内容整理=================================================

SQL structed query language

连接MYSQL服务器：mysql -uroot -proot

Database Server :
Database(DB)
Table

DDL (Data Definition Language )
create
alter
drop

DML:(Data Manipulation Language）
insert into
delete from
update
select

表的一行（row）称之为一条记录
表中一条记录对应一个java对象的数据
表的一列（column）称之为一个字段

１、Java是使用对象封装数据，例如程序产生了如上所示２个user对象，这些对象的数据要想保存到数据库中，需要在数据库中创建与之对应的表，一个user对象中封装的数据，要保存到数据库中，一般就要在数据库中创建一个与之对应的表。
２、对象的属性定义为表头，对象的数据对应于表中的一条记录。
３、每个对象对应于表中的一条记录。

数据库的操作：创建，查看，修改，删除
*创建：
创建一个名称为mydb1的数据库。
create database mydb1;

创建一个使用utf-8字符集的mydb2数据库。
create database mydb2 character set utf8;

创建一个使用utf-8字符集，并带校对规则的mydb3数据库。
create database mydb2 character set utf8 collate utf8_general_ci;

*查看:
显示所有数据库
show databases;

显示创建数据库的语句信息
show create database mydb2;

*修改:
修改mydb1的字符集为gbk(不能修改数据库名)
alter database mydb1 character set utf8;

*删除:
删除数据库mydb2
drop database mydb1;

表的操作：创建，查看，修改，删除
*创建：
根据实体类Person创建表person
Person {
int id;
String name;
}

create table person(
id int,
name varchar(20)
);

mysql中的数据类型：
bit 1位　但可以指定位数，如：bit<3>
int 2字节可以指定最大位数，如：int<4>　最大为4位的整数
float 2个字节　可以指定最大的位数和最大的小数位数，如：float<5,2> 最大为一个５位的数，小数位最多2位
double　4个字节　可以指定最大的位数和最大的小数位数，如：float<6,4> 最大为一个6位的数，小数位最多4位
char　必须指定字符数,如char(5) 为不可变字符　即使存储的内容为'ab',也是用5个字符的空间存储这个数据
varchar　必须指定字符数,如varchar(5) 为可变字符　如果存储的内容为'ab',占用2个字符的空间；如果为'abc',则占用3个字符的空间
text: 大文本(大字符串)
blob：二进制大数据　如图片，音频文件，视频文件
date: 日期　如：'1921-01-02'
datetime: 日期时间　如：'1921-01-02 12:23:43'
timeStamp: 时间戳，自动赋值为当前日期时间

DATETIME 日期和时间的组合。支持的范围是'1000-01-01 00:00:00'到'9999-12-31 23:59:59'。MySQL以'YYYY-MM-DD HH:MM:SS'格式显示DATETIME值，但允许使用字符串或数字为DATETIME列分配值。
TIMESTAMP[(M)] 时间戳。范围是'1970-01-01 00:00:00'到2037年。 TIMESTAMP列用于INSERT或UPDATE操作时记录日期和时间。如果你不分配一个值，表中的第一个TIMESTAMP列自动设置为最近操作的日期和时间。也可以通过分配一个NULL值，将TIMESTAMP列设置为当前的日期和时间。 TIMESTAMP值返回后显示为'YYYY-MM-DD HH:MM:SS'格式的字符串，显示宽度固定为19个字符。如果想要获得数字值，应在TIMESTAMP 列添加+0。

创建一个员工表
create table employee(
id int,
name varchar(20),
sex bit,
birthday date,
entry_date date,
job varchar(20),
salary double,
resume text
);

*查看：
查看所有的表：
show tables;

查看指定表的创建语句
show create table employee;

显示指定表的结构：
desc employee;

*删除：
删除employee表
drop table employee;

*修改表：
增加一个字段：alter table worker add column height double;
修改一个字段：alter table worker modify column height float;
删除一个字段：alter table worker drop column height;
更改表名：rename table employee to worker;
修改表的字符集:alter table worker character set gbk;

表数据的CRUD
CRUD操作：指在做计算处理时的增加(Create)、查询(Retrieve)、更新(Update)和删除(Delete)

*C(create增加数据) Insert语句：
注意：字符和日期型数据应包含在单引号中。
show variables like 'character%';
mysql -uroot -proot --default_character_set=gbk

新建Employee表并表中添加一些记录
create table employee(
id int,
name varchar(20),
sex bit,
birthday date,
salary double,
entry_date date,
resume text
);
insert into employee(name,id,sex,birthday,salary,entry_date,resume) values('张三',1,1,'1983-09-21',15000,'2012-06-24','一个大牛');
insert into employee(id,name,sex,birthday,salary,entry_date,resume) values(2,'李四',1,'1984-09-21',10000,'2012-07-24','一个中牛');
insert into employee(id,name,sex,birthday,salary,entry_date,resume) values(3,'王五',0,'1985-09-21',7000,'2012-08-24','一个小牛');

*U(update更新数据) Update语句：
将所有员工薪水都增加500元。
update employee set salary=salary+500;
将王五的员工薪水修改为10000元，resume改为也是一个中牛
update employee set salary=10000,resume='也是一个中牛' where name='王五';

*D(drop删除数据) Delete语句：
删除表中姓名为王五的记录。
delete from employee where name='王五';
删除表中所有记录。
delete from employee; --可以有条件，但删除所有记录差了一点
使用truncate删除表中记录。
truncate employee;--无条件效率高

*R(Retrieve查找数据) Select语句：
准备环境：使用 SQLyog_Enterprise，企业版软件。
create table student(
id int,
name varchar(20),
chinese int,
english int,
math int
);

insert into student(id,name,chinese,english,math) values(1,'何东',80,85,90);
insert into student(id,name,chinese,english,math) values(2,'权金属',90,95,95);
insert into student(id,name,chinese,english,math) values(3,'何南',80,96,96);
insert into student(id,name,chinese,english,math) values(4,'叶子',81,97,85);
insert into student(id,name,chinese,english,math) values(5,'何西',85,84,90);
insert into student(id,name,chinese,english,math) values(6,'丁香',92,85,87);
insert into student(id,name,chinese,english,math) values(7,'何北',75,81,80);
insert into student(id,name,chinese,english,math) values(8,'唐中',77,80,79);
insert into student(id,name,chinese,english,math) values(9,'任已',95,85,85);
insert into student(id,name,chinese,english,math) values(10,'王八',94,85,84);

//关键字：select from where distinct
查询表中所有学生的信息。
select * from student;
查询表中所有学生的姓名和对应的英语成绩。
select name,english from student;
过滤表中重复数据。
select english from student;
select DISTINCT english from student;
select DISTINCT english,name from student;

select english+chinese+math from student;
select english+chinese+math as 总分 from student;
select name,english+chinese+math as 总分 from student;

//关键字 as 别名
在所有学生英语分数上加10分特长分。
select name,english+10 from student;
统计每个学生的总分。
select english+chinese+math from student;
使用别名表示学生分数
select name,english+chinese+math as 总分 from student;
select name,english+chinese+math 总分 from student;

//关键字：select from where
查询姓名为何东的学生成绩
select * from student where name='何东';
查询英语成绩大于90分的同学
select * from student where english>90;
查询总分大于250分的所有同学
select * from student where english+chinese+math>250;

查询英语分数在 85－95之间的同学。
select * from student whereenglish>=85 and english<=95;
select * from student where english between 85 and 95;
查询数学分数为84,90,91的同学。
select * from student where math=84 or math=90 or math=91;
select * from student where math in(84,90,91);
查询所有姓何的学生成绩。
select * from student where name like '何%';
select * from student where name like '何_%';
注意：Like语句中，% 代表零个或多个任意字符，_ 代表一个字符，例first_name like ‘_a%’;
查询数学分>85，语文分>90的同学。
select * from student where math>85 and chinese>90;

//关键字 order by(默认为升序) desc为降序 asc 升序别名 as
对数学成绩排序后输出。
select * from student order by math;
对总分排序后输出，然后再按从高到低的顺序输出
select * from student order by math+chinese+english desc;
select name, math+chinese+english as sumScroe from student order by sumScroe desc;
对姓何的学生成绩排序输出
select * from student where name like '何%' order by math+chinese+english desc;
select name, math+chinese+english from student where name like '何%' order by math+chinese+english desc;

//关键字 count
统计一个班级共有多少学生？
select count(*) from student;
统计数学成绩大于90的学生有多少个？
select count(*) from student where math>90;
统计总分大于250的人数有多少？
select count(*) from student where math+chinese+english>250;

//关键字 sum
统计一个班级数学总成绩？
select sum(math) from student;
统计一个班级语文、英语、数学各科的总成绩
select sum(math), sum(chinese), sum(english) from student;
统计一个班级语文、英语、数学的成绩总和
select sum(math+chinese+english)from student;
select sum(math)+sum(chinese)+sum(english) from student;

//关键字 avg
求一个班级数学平均分？
select avg(math) from student;
求一个班级总分平均分
select avg(math+chinese+english)from student;
select avg(math)+avg(chinese)+avg(english) from student;

//关键字 max min
求班级最高分和最低分
select max(math+chinese+english),min(math+chinese+english) from student;

//关键字 group by having
查出各个班的总分，最高分
使用group by 子句对列进行分组
Having和where均可实现过滤，但在having可以使用合计函数,having通常跟在group by后，它作用于组。
准备环境：使用 SQLyog_Enterprise，企业版。
给表添加一个字段：alter table student add column class_id int;
更新表：
update student set class_id=1 where id<=5;
update student set class_id=2 where id>5;
select sum(math+chinese+english),max(math+chinese+english) from student group by class_id;

查询出班级总分大于1300分的班级ID
select class_id from student group by class_id having sum(math+chinese+english)>1300;

表的约束　　
*定义主键约束　primary key:不允许为空，不允许重复

*定义主键自动增长　auto_increment

*定义唯一约束　unique

*定义非空约束　not null

*定义外键约束　constraint ordersid_FK foreign key(ordersid) references orders(id)

*删除主键：alter table tablename drop primary key ;

CREATE TABLE user(
id INT PRIMARY KEY AUTO_INCREMENT, #主键，自增长
name VARCHAR(20) UNIQUE, #不可重复
password VARCHAR(15) NOT NULL #不允许为空
)

insert into user(name, password) values('MM', NULL);#执行不通过Column 'password' cannot be null
insert into user(name, password) values('MM', '123456');#通过
insert into user(name, password) values('MM', '123sdfd');#执行不通过Duplicate entry 'MM' for key 'name'

//测试外键
准备环境：
创建一个班级表：

create table class(
id int primary key auto_increment,
name varchar(16)

);

create table student(
id int(11) primary key auto_increment default null,
name varchar(20) default null,
chinese int(11) default null,
english int(11) default null,
math int(11) default null,
classid int(11) default null,
constraint student_classid_FK foreign key(classid) references class(id)
);

insert into class(name) values('三年一班');
insert into class(name) values('三年二班');

insert into student(name, classid) values('tom', 3); #classid的值只能是被引用的字段的某个值
insert into student(name, classid) values('tom', 2);

delete from class where id=2; #删除被引用的记录无法成功
select * from class;
select * from student;

数据的备份与恢复：
*准备数据：
create database mydb1;
use mydb1;
create table user(
id int,
name varchar(20)
);

insert into user(id,name) values(1,'Tom');
select * from user;

*备份backup export：
mysqldump -uroot -p mydb1>d:\test.sql;--备份数据库里的数据
Mysqldump -uroot -proot mydb1 > test_backup.sql

*恢复 import:
mysql -uroot -p mydb1<d:\test.sql
source d:\test.sql(在mysql客户端上执行，需要选中use要导进的库)

多表查询与子查询：
准备环境：
部门表
CREATE TABLE DEPARTMENT(
department_id int primary key auto_increment,
name varchar(20)
);

职位表
CREATE TABLE LOCATION (
location_id int PRIMARY KEY auto_increment,
name varchar(15)
);

员工表
CREATE TABLE EMPLOYEES(
employee_id int PRIMARY KEY auto_increment,
department_id int,
location_id int,
first_name varchar(10),
last_name varchar(10),
salary double,
hire_date date,
constraint employees_department_id_FK foreign key(department_id) references department(department_id),
constraint employees_location_id_FK foreign key(location_id) references location(location_id)
);

向department表中添加数据
insert into department(name) values ('人事');
insert into department(name) values ('财务');
insert into department(name) values ('后勤');
insert into department(name) values ('公关');
insert into department(name) values ('研发');

向location表中添加数据
insert into location(name) values ('总经理');
insert into location(name) values ('经理');
insert into location(name) values ('主管');
insert into location(name) values ('组长');
insert into location(name) values ('职员');

向employees表中添加数据
insert into employees(department_id,location_id , first_name, last_name, salary,hire_date)
values (1,1, 'A', 'z', 50000, '2005-02-21');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (1,2, 'B', 'x', 20000, '2009-03-21');
insert into employees(department_id,location_id , first_name, last_name, salary,hire_date)
values (2,3, 'C', 'v', 10000, '2009-08-23');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (4,2, 'D', 'n', 30000, '2004-09-28');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (3,5, 'E', 'm', 3000, '2009-04-11');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (5,5, 'F', 'l', 5000, '2008-03-11');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (5,3, 'G', 'p', 20000, '2005-05-09');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (5,4, 'H', 'o', 8000, '2006-07-21');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (5,5, 'I', 'u', 6000, '2006-09-21');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (5,5, 'J', 'y', 5500, '2007-08-21');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (5,5, 'K', 't', 6500, '2006-12-21');
insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)
values (5,1, 'L', 'r', 100000, '2001-05-21');
练习：
--多表查询：查出姓z的员工的所有信息（使用别名）#联表查询
select * from employees e, department d, location l
where e.[department_id]=d.[department_id] and e.[location_id]=l.[location_id] and e.[last_name]='z';
select * from employees e, department d, location l where e.department_id=d.department_id and e.location_id=l.location_id and e.last_name='z';

--单行子查询: 查出所有工资大于平均工资的员工信息
select * from employees where salary >(select avg(salary) from employees)

--多行子查询: 查出所有所有姓z的部门名称
先得到部门ID：select department_id from employees where last_name='z'
select name from department where department_id in (select department_id from employees where last_name='z');

SQL structed query language连接MYSQL服务器：mysql -uroot -prootDatabase Server : Database(DB)TableDDL (Data Definition Language )createalterdropDML:(Data Manipulation Language） insert intodelete from updateselect 表的一行（row）称之为一条记录表中一条记录对应一个java对象的数据表的一列（column）称之为一个字段１、Java是使用对象封装数据，例如程序产生了如上所示２个user对象，这些对象的数据要想保存到数据库中，需要在数据库中创建与之对应的表，一个user对象中封装的数据，要保存到数据库中，一般就要在数据库中创建一个与之对应的表。２、对象的属性定义为表头，对象的数据对应于表中的一条记录。３、每个对象对应于表中的一条记录。数据库的操作：创建，查看，修改，删除*创建：创建一个名称为mydb1的数据库。create database mydb1;创建一个使用utf-8字符集的mydb2数据库。create database mydb2 character set utf8;创建一个使用utf-8字符集，并带校对规则的mydb3数据库。create database mydb2 character set utf8 collate utf8_general_ci;*查看:显示所有数据库show databases;显示创建数据库的语句信息show create database mydb2;*修改:修改mydb1的字符集为gbk(不能修改数据库名)alter database mydb1 character set utf8;*删除:删除数据库mydb2drop database mydb1;表的操作：创建，查看，修改，删除*创建：根据实体类Person创建表personPerson {int id;String name;}create table person(id int,name varchar(20));mysql中的数据类型：bit 1位　但可以指定位数，如：bit<3>int 2字节 可以指定最大位数，如：int<4>　最大为4位的整数float 2个字节　可以指定最大的位数和最大的小数位数，如：float<5,2> 最大为一个５位的数，小数位最多2位double　4个字节　可以指定最大的位数和最大的小数位数，如：float<6,4> 最大为一个6位的数，小数位最多4位char　必须指定字符数,如char(5) 为不可变字符　即使存储的内容为'ab',也是用5个字符的空间存储这个数据varchar　必须指定字符数,如varchar(5) 为可变字符　如果存储的内容为'ab',占用2个字符的空间；如果为'abc',则占用3个字符的空间text: 大文本(大字符串)blob：二进制大数据　如图片，音频文件，视频文件date: 日期　如：'1921-01-02'datetime: 日期时间　如：'1921-01-02 12:23:43'timeStamp: 时间戳，自动赋值为当前日期时间DATETIME 日期和时间的组合。支持的范围是'1000-01-01 00:00:00'到'9999-12-31 23:59:59'。MySQL以'YYYY-MM-DD HH:MM:SS'格式显示DATETIME值，但允许使用字符串或数字为DATETIME列分配值。 TIMESTAMP[(M)] 时间戳。范围是'1970-01-01 00:00:00'到2037年。 TIMESTAMP列用于INSERT或UPDATE操作时记录日期和时间。如果你不分配一个值，表中的第一个TIMESTAMP列自动设置为最近操作的日期和时间。也可以通过分配一个NULL值，将TIMESTAMP列设置为当前的日期和时间。 TIMESTAMP值返回后显示为'YYYY-MM-DD HH:MM:SS'格式的字符串，显示宽度固定为19个字符。如果想要获得数字值，应在TIMESTAMP 列添加+0。 创建一个员工表create table employee(id int,name varchar(20),sex bit,birthday date,entry_date date,job varchar(20),salary double,resume text);*查看：查看所有的表：show tables;查看指定表的创建语句show create table employee;显示指定表的结构：desc employee;*删除：删除employee表drop table employee;*修改表：增加一个字段：alter table worker add column height double;修改一个字段：alter table worker modify column height float;删除一个字段：alter table worker drop column height;更改表名：rename table employee to worker;修改表的字符集:alter table worker character set gbk;表数据的CRUDCRUD操作：指在做计算处理时的增加(Create)、查询(Retrieve)、更新(Update)和删除(Delete) *C(create增加数据) Insert语句 ：注意：字符和日期型数据应包含在单引号中。show variables like 'character%';mysql -uroot -proot --default_character_set=gbk新建Employee表并表中添加一些记录create table employee(id int,name varchar(20),sex bit,birthday date,salary double,entry_date date,resume text);insert into employee(name,id,sex,birthday,salary,entry_date,resume) values('张三',1,1,'1983-09-21',15000,'2012-06-24','一个大牛');insert into employee(id,name,sex,birthday,salary,entry_date,resume) values(2,'李四',1,'1984-09-21',10000,'2012-07-24','一个中牛');insert into employee(id,name,sex,birthday,salary,entry_date,resume) values(3,'王五',0,'1985-09-21',7000,'2012-08-24','一个小牛');*U(update更新数据) Update语句 ：将所有员工薪水都增加500元。update employee set salary=salary+500;将王五的员工薪水修改为10000元，resume改为也是一个中牛update employee set salary=10000,resume='也是一个中牛' where name='王五';*D(drop删除数据) Delete语句 ：删除表中姓名为王五的记录。delete from employee where name='王五';删除表中所有记录。delete from employee; --可以有条件，但删除所有记录差了一点使用truncate删除表中记录。truncate employee;--无条件 效率高*R(Retrieve查找数据) Select语句：准备环境：使用 SQLyog_Enterprise，企业版。create table student(id int,name varchar(20),chinese int,english int,math int);insert into student(id,name,chinese,english,math) values(1,'何东',80,85,90);insert into student(id,name,chinese,english,math) values(2,'权金属',90,95,95);insert into student(id,name,chinese,english,math) values(3,'何南',80,96,96);insert into student(id,name,chinese,english,math) values(4,'叶子',81,97,85);insert into student(id,name,chinese,english,math) values(5,'何西',85,84,90);insert into student(id,name,chinese,english,math) values(6,'丁香',92,85,87);insert into student(id,name,chinese,english,math) values(7,'何北',75,81,80);insert into student(id,name,chinese,english,math) values(8,'唐中',77,80,79);insert into student(id,name,chinese,english,math) values(9,'任已',95,85,85);insert into student(id,name,chinese,english,math) values(10,'王八',94,85,84);//关键字：select from where distinct查询表中所有学生的信息。select * from student;查询表中所有学生的姓名和对应的英语成绩。select name,english from student;过滤表中重复数据。select english from student;select DISTINCT english from student;select DISTINCT english,name from student;select english+chinese+math from student;select english+chinese+math as 总分 from student;select name,english+chinese+math as 总分 from student;//关键字 as在所有学生英语分数上加10分特长分。select name,english+10 from student;统计每个学生的总分。select english+chinese+math from student;使用别名表示学生分数select name,english+chinese+math as 总分 from student;select name,english+chinese+math 总分 from student;//关键字：where查询姓名为何东的学生成绩select * from student where name='何东';查询英语成绩大于90分的同学select * from student where english>90;查询总分大于250分的所有同学select * from student where english+chinese+math>250;查询英语分数在 85－95之间的同学。select * from student whereenglish>=85 and english<=95;select * from student where english between 85 and 95;查询数学分数为84,90,91的同学。select * from student where math=84 or math=90 or math=91;select * from student where math in(84,90,91);查询所有姓何的学生成绩。select * from student where name like '何%';select * from student where name like '何_%';注意：Like语句中，% 代表零个或多个任意字符，_ 代表一个字符，例first_name like ‘_a%’;查询数学分>85，语文分>90的同学。select * from student where math>85 and chinese>90;//关键字 order by(默认为升序)   desc为降序   asc 升序   别名 as对数学成绩排序后输出。select * from student order by math;对总分排序后输出，然后再按从高到低的顺序输出select * from student order by math+chinese+english desc;select  name, math+chinese+english as sumScroe from student order by sumScroe  desc;对姓何的学生成绩排序输出select * from student where name like '何%' order by math+chinese+english desc;select name, math+chinese+english from student where name like '何%' order by math+chinese+english desc;//关键字 count统计一个班级共有多少学生？select count(*) from student;统计数学成绩大于90的学生有多少个？select count(*) from student where math>90;统计总分大于250的人数有多少？select count(*) from student where math+chinese+english>250;//关键字 sum统计一个班级数学总成绩？select sum(math) from student;统计一个班级语文、英语、数学各科的总成绩select sum(math), sum(chinese), sum(english) from student;统计一个班级语文、英语、数学的成绩总和select sum(math+chinese+english)from student;select sum(math)+sum(chinese)+sum(english) from student;//关键字 avg求一个班级数学平均分？select avg(math) from student;求一个班级总分平均分select avg(math+chinese+english)from student;select avg(math)+avg(chinese)+avg(english) from student;//关键字 max  min求班级最高分和最低分select max(math+chinese+english),min(math+chinese+english) from student;//关键字 group by  having查出各个班的总分，最高分使用group by 子句对列进行分组Having和where均可实现过滤，但在having可以使用合计函数,having通常跟在group by后，它作用于组。准备环境：使用 SQLyog_Enterprise，企业版。给表添加一个字段：alter table student add column class_id int;更新表：update student set class_id=1 where id<=5;update student set class_id=2 where id>5;select sum(math+chinese+english),max(math+chinese+english) from student group by class_id;查询出班级总分大于1300分的班级IDselect class_id from student group by class_id having sum(math+chinese+english)>1300;表的约束　　*定义主键约束　primary key:不允许为空，不允许重复*定义主键自动增长　auto_increment*定义唯一约束　unique*定义非空约束　not null*定义外键约束　constraint ordersid_FK foreign key(ordersid) references orders(id)*删除主键：alter table tablename drop primary key ;CREATE TABLE user(id INT PRIMARY KEY AUTO_INCREMENT, #主键，自增长name VARCHAR(20) UNIQUE, #不可重复password VARCHAR(15) NOT NULL #不允许为空)insert into user(name, password) values('MM', NULL);#执行不通过Column 'password' cannot be nullinsert into user(name, password) values('MM', '123456');#通过insert into user(name, password) values('MM', '123sdfd');#执行不通过Duplicate entry 'MM' for key 'name'//测试外键准备环境：创建一个班级表：create table class(id int primary key auto_increment,name varchar(16));create table student(id  int(11) primary key auto_increment default null,name varchar(20) default null,chinese int(11) default null,english int(11) default null,math int(11) default null,classid int(11) default null,constraint student_classid_FK foreign key(classid) references class(id));insert into class(name) values('三年一班');insert into class(name) values('三年二班');insert into student(name, classid) values('tom', 3); #classid的值只能是被引用的字段的某个值insert into student(name, classid) values('tom', 2);delete from class where id=2; #删除被引用的记录无法成功select * from class;select * from student;数据的备份与恢复：*准备数据：create database mydb1;use mydb1;create table user(id int,name varchar(20));insert into user(id,name) values(1,'Tom');select * from user;*备份：mysqldump -uroot -p mydb1>d:\test.sql;--备份数据库里的数据Mysqldump -uroot -proot mydb1 > test_backup.sql*恢复；mysql -uroot -p mydb1<d:\test.sqlsource d:\test.sql(在mysql客户端上执行，需要选中use要导进的库)多表查询与子查询：准备环境：部门表CREATE TABLE DEPARTMENT(   department_id int primary key auto_increment,          name varchar(20));职位表CREATE TABLE LOCATION (   location_id int PRIMARY KEY auto_increment,          name varchar(15));员工表CREATE TABLE EMPLOYEES(   employee_id int PRIMARY KEY auto_increment,          department_id int,          location_id int,          first_name varchar(10),          last_name varchar(10),          salary double,   hire_date date,   constraint employees_department_id_FK foreign key(department_id) references department(department_id),   constraint employees_location_id_FK foreign key(location_id) references location(location_id));向department表中添加数据 insert into department(name) values ('人事');insert into department(name) values ('财务');insert into department(name) values ('后勤');insert into department(name) values ('公关');insert into department(name) values ('研发');向location表中添加数据insert into location(name) values ('总经理');insert into location(name) values ('经理');insert into location(name) values ('主管');insert into location(name) values ('组长');insert into location(name) values ('职员');向employees表中添加数据insert into employees(department_id,location_id , first_name, last_name, salary,hire_date)   values (1,1, 'A', 'z', 50000, '2005-02-21');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (1,2, 'B', 'x', 20000, '2009-03-21');       insert into employees(department_id,location_id , first_name, last_name, salary,hire_date)   values (2,3, 'C', 'v', 10000, '2009-08-23');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (4,2, 'D', 'n', 30000, '2004-09-28');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (3,5, 'E', 'm', 3000, '2009-04-11');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (5,5, 'F', 'l', 5000, '2008-03-11');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (5,3, 'G', 'p', 20000, '2005-05-09');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (5,4, 'H', 'o', 8000, '2006-07-21');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (5,5, 'I', 'u', 6000, '2006-09-21');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (5,5, 'J', 'y', 5500, '2007-08-21');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (5,5, 'K', 't', 6500, '2006-12-21');       insert into employees(department_id,location_id, first_name, last_name, salary,hire_date)   values (5,1, 'L', 'r', 100000, '2001-05-21'); 练习：--多表查询：查出姓z的员工的所有信息（使用别名）#联表查询select * from employees e, department d, location l where e.[department_id]=d.[department_id] and e.[location_id]=l.[location_id] and e.[last_name]='z';select * from employees e, department d, location l where e.department_id=d.department_id and e.location_id=l.location_id and e.last_name='z';--单行子查询: 查出所有工资大于平均工资的员工信息 select * from employees where salary >(select avg(salary) from employees) --多行子查询: 查出所有所有姓z的部门名称 先得到部门ID：select department_id from employees where last_name='z'select name from department where department_id in (select department_id from employees where last_name='z');