第3章 MySQL常用增，删，改，查，用户授权，备份，等操作

 在MySQL中最基础运用的就是增删改查命令，这篇文章我将详细的介绍mysqi的基础命令。

首先我们来了解一下SQL结构化查询语言：它是一种关系型数据库中的数据进行定义和操作的语言方法。

SQL结构化查询语言重要的几种：

•  DQL (数据查询语言)：用以从表中获得数据，确定数据怎样在应用程序给出的。

            例如：(select)。

•  DDL（数据定义语言）：用于创建新表或者删除表，为表加索引等操作。

           例如：create，drop

•  DML (数据操作语言)：用于添加，修改，删除表中的行或者数据

           例如：insert,update,delete

•  DCL：数据控制语言：它通过语句grant或者revoke获得允许。

下面我们来具体看怎样使用这些语言：

1.登录方式

mysql的登陆方式有三种，如下：

•  mysql
•  mysql -uroot
•  mysql -uroot -pzxc123

• [root@mysql mysql-5.5.22]# mysql -uroot -p123123
  Welcome to the MariaDB monitor.  Commands end with ; or g.
  Your MySQL connection id is 3
  Server version: 5.5.22-log Source distribution
  
  Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
  
  Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
  
  MySQL [(none)]>　　

2. 登录后会有MySQL [(none)]>的提示符，下面我们来修改一下自己的命令提示符：prompt命令

•  

  MySQL [(none)]> prompt u@Carrie ->
  PROMPT set to 'u@Carrie ->'
  
  root@Carrie ->
  

  　　

3.　　 退出MySQL的方式

• quit
• ctrl+c 
• ctrl +d

4.修改密码

       第一种方式

• mysqladmin -uroot -p123123 password zxc123
•  

  [root@mysql ~]# mysqladmin -uroot -p123123 password zxc123
  [root@mysql ~]# mysql -uroot -p123123
  ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
  [root@mysql ~]# mysql -uroot -pzxc123
  Welcome to the MariaDB monitor.  Commands end with ; or g.
  Your MySQL connection id is 7
  Server version: 5.5.22-log Source distribution
  
  Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
  
  Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
  
  MySQL [(none)]> 
  

  　　

 第二种方式

• 在数据库中修改命令 

• 错误示范：因为密码是加密的，这么直接修改。密码还是用不了。切记
  MySQL [Carrie]> select user,host,password from mysql.user;
  +------+-----------+-------------------------------------------+
  | user | host      | password                                  |
  +------+-----------+-------------------------------------------+
  | root | localhost | *E56A114692FE0DE073F9A1DD68A00EEB9703F3F1 |
  | root | mysql     |                                           |
  | root | 127.0.0.1 |                                           |
  | root | ::1       |                                           |
  |      | localhost |                                           |
  |      | mysql     |                                           |
  +------+-----------+-------------------------------------------+
  6 rows in set (0.00 sec)
  
  MySQL [Carrie]> update mysql.user set password='zxc123' where host='localhost';
  Query OK, 2 rows affected (0.00 sec)
  Rows matched: 2  Changed: 2  Warnings: 0
  
  

  正确示范：加一个函数，让其有加密算法

• MySQL [Carrie]> update mysql.user set password=password(123123) where host='localhost';
  Query OK, 2 rows affected (0.00 sec)
  Rows matched: 2  Changed: 2  Warnings: 0
  
  MySQL [Carrie]> select  user,host,password from mysql.user;
  +------+-----------+-------------------------------------------+
  | user | host      | password                                  |
  +------+-----------+-------------------------------------------+
  | root | localhost | *E56A114692FE0DE073F9A1DD68A00EEB9703F3F1 |
  | root | mysql     |                                           |
  | root | 127.0.0.1 |                                           |
  | root | ::1       |                                           |
  |      | localhost | *E56A114692FE0DE073F9A1DD68A00EEB9703F3F1 |
  |      | mysql     |                                           |
  +------+-----------+-------------------------------------------+
  6 rows in set (0.00 sec)
  

 第三种方法：直接用set解决

• MySQL [Carrie]> set password=password('123123') ;
  Query OK, 0 rows affected (0.00 sec)

5.创建一个数据库

用create创建数据库

• MySQL [(none)]> create database Carrie;
  Query OK, 1 row affected (0.00 sec)
  

•  数据库默认拉丁文，如果想加中文创建数据库时需要添加charset,例如：

• MySQL [Carrie]> create table hanjiali (id int(3),name varchar(10)) default charset =utf8;
  Query OK, 0 rows affected (0.00 sec)

  MySQL [Carrie]> insert into hanjiali values (1,'韩佳丽');
  Query OK, 1 row affected (0.00 sec)
  
  MySQL [Carrie]> select * from hanjiali;
  +------+-----------+
  | id   | name      |
  +------+-----------+
  |    1 | 韩佳丽    |
  +------+-----------+
  1 row in set (0.00 sec)
  

  　　

6.查看数据库

用show 查看数据库

• MySQL [(none)]> show databases;
  +--------------------+
  | Database           |
  +--------------------+
  | information_schema |
  | Carrie             |
  | mysql              |
  | performance_schema |
  | test               |
  +--------------------+
  5 rows in set (0.00 sec)　　

7.使用数据库

用use使用数据库

• MySQL [(none)]> use Carrie;
  Database changed
  MySQL [Carrie]>
  

  　　

8.删除数据库Carrie

用drop删除数据库

• MySQL [Carrie]> drop database Carrie;
  Query OK, 0 rows affected (0.00 sec)
  

  　　

9.创建数据库中的表

用creat创建表

• MySQL [Carrie]> create table student (id int(3),name varchar(10),age int(3));
  Query OK, 0 rows affected (0.00 sec)
  

  　　

10.查看表字段

表字段就是表中的结构，也是表中的表头信息。

用 desc查看表字段

• MySQL [Carrie]> desc student;
  +-------+-------------+------+-----+---------+-------+
  | Field | Type        | Null | Key | Default | Extra |
  +-------+-------------+------+-----+---------+-------+
  | id    | int(3)      | YES  |     | NULL    |       |
  | name  | varchar(10) | YES  |     | NULL    |       |
  | age   | int(3)      | YES  |     | NULL    |       |
  +-------+-------------+------+-----+---------+-------+
  3 rows in set (0.00 sec)
  

  　　

11.删除表

用drop删除表

• MySQL [Carrie]> drop table student;
  Query OK, 0 rows affected (0.00 sec)
  

  　　

12.对表结构的增删改方法

• 添加入表字段，用alter table 表名 add进行添加        

• MySQL [Carrie]> alter table student add sex varchar(5);
  Query OK, 0 rows affected (0.00 sec)
  Records: 0  Duplicates: 0  Warnings: 0
  

  　　

• 添加表字段还可以选定添加的位置，如下 

• MySQL [Carrie]> alter table student add code int(10) after id;
  Query OK, 0 rows affected (0.01 sec)
  Records: 0  Duplicates: 0  Warnings: 0
  

  　　

• 表结构最终成型如下

• MySQL [Carrie]> desc student;
  +-------+-------------+------+-----+---------+-------+
  | Field | Type        | Null | Key | Default | Extra |
  +-------+-------------+------+-----+---------+-------+
  | id    | int(3)      | YES  |     | NULL    |       |
  | code  | int(10)     | YES  |     | NULL    |       |
  | name  | varchar(10) | YES  |     | NULL    |       |
  | age   | int(3)      | YES  |     | NULL    |       |
  | sex   | varchar(5)  | YES  |     | NULL    |       |
  +-------+-------------+------+-----+---------+-------+
  5 rows in set (0.00 sec)
  

  　　

• 删除表结构中的内容

• MySQL [Carrie]> alter table student drop code;
  Query OK, 0 rows affected (0.01 sec)
  Records: 0  Duplicates: 0  Warnings: 0
  
  MySQL [Carrie]> desc student;
  +-------+-------------+------+-----+---------+-------+
  | Field | Type        | Null | Key | Default | Extra |
  +-------+-------------+------+-----+---------+-------+
  | id    | int(3)      | YES  |     | NULL    |       |
  | name  | varchar(10) | YES  |     | NULL    |       |
  | age   | int(3)      | YES  |     | NULL    |       |
  | sex   | varchar(5)  | YES  |     | NULL    |       |
  +-------+-------------+------+-----+---------+-------+
  4 rows in set (0.00 sec)
  

  　　

• 修改表结构的类型

• MySQL [Carrie]> desc student;
  +-------+-------------+------+-----+---------+-------+
  | Field | Type        | Null | Key | Default | Extra |
  +-------+-------------+------+-----+---------+-------+
  | id    | int(3)      | YES  |     | NULL    |       |
  | name  | varchar(10) | YES  |     | NULL    |       |
  | age   | int(3)      | YES  |     | NULL    |       |
  | sex   | varchar(5)  | YES  |     | NULL    |       |
  +-------+-------------+------+-----+---------+-------+
  4 rows in set (0.00 sec)
  
  MySQL [Carrie]> alter table student modify age int(10);
  Query OK, 0 rows affected (0.00 sec)
  Records: 0 Duplicates: 0 Warnings: 0
  
  MySQL [Carrie]> desc student;
  
  +-------+-------------+------+-----+---------+-------+
  | Field | Type        | Null | Key | Default | Extra |
  +-------+-------------+------+-----+---------+-------+
  | id    | int(3)      | YES  |     | NULL    |       |
  | name  | varchar(10) | YES  |     | NULL    |       |
  | age   | int(10)     | YES  |     | NULL    |       |
  | sex   | varchar(5)  | YES  |     | NULL    |       |
  +-------+-------------+------+-----+---------+-------+
  4 rows in set (0.00 sec)
  

  　　

• 修改表结构的名称

• MySQL [Carrie]> alter table student change name name_student varchar(10);
  Query OK, 0 rows affected (0.00 sec)
  Records: 0  Duplicates: 0  Warnings: 0
  
  MySQL [Carrie]> desc student;
  +--------------+-------------+------+-----+---------+-------+
  | Field        | Type        | Null | Key | Default | Extra |
  +--------------+-------------+------+-----+---------+-------+
  | id           | int(3)      | YES  |     | NULL    |       |
  | name_student | varchar(10) | YES  |     | NULL    |       |
  | age          | int(10)     | YES  |     | NULL    |       |
  | sex          | varchar(5)  | YES  |     | NULL    |       |
  +--------------+-------------+------+-----+---------+-------+
  4 rows in set (0.00 sec)
  

  　　

13.修改表名

• MySQL [Carrie]> alter table student rename to student_data;
  Query OK, 0 rows affected (0.00 sec)
  
  MySQL [Carrie]> desc student;
  ERROR 1146 (42S02): Table 'Carrie.student' doesn't exist
  MySQL [Carrie]> desc student_data;
  +--------------+-------------+------+-----+---------+-------+
  | Field        | Type        | Null | Key | Default | Extra |
  +--------------+-------------+------+-----+---------+-------+
  | id           | int(3)      | YES  |     | NULL    |       |
  | name_student | varchar(10) | YES  |     | NULL    |       |
  | age          | int(10)     | YES  |     | NULL    |       |
  | sex          | varchar(5)  | YES  |     | NULL    |       |
  +--------------+-------------+------+-----+---------+-------+
  4 rows in set (0.00 sec
  

14.对表中数据进行增删改查

• 插入表中的数据

• MySQL [Carrie]> insert into student_data (id,name_student,age,sex) values (1,'Carrie',18,'woman');
  Query OK, 1 row affected (0.00 sec)

  MySQL [Carrie]> insert into student_data values (3,'Matin',20,'man');
  Query OK, 1 row affected (0.00 sec)

  此处用了了两种方式插入表信息

•  查看表中数据

• MySQL [Carrie]> select * from student_data;
  +------+--------------+------+-------+
  | id | name_student | age | sex |
  +------+--------------+------+-------+
  | 1 | Carrie | 18 | woman |
  | 2 | Susie | 19 | woman |
  | 3 | Montin | 20 | man |
  | 2 | Susie | 18 | woman |
  | 3 | Matin | 20 | man |
  +------+--------------+------+-------+
  5 rows in set (0.00 sec)

•  删除表中数据

• MySQL [Carrie]> delete from student_data where id=3;
  
  Query OK, 2 rows affected (0.00 sec)
  
  MySQL [Carrie]> select * from student_data;
  +------+--------------+------+-------+
  | id   | name_student | age  | sex    |
  +------+--------------+------+-------+
  |    1 | Carrie        |   18 | woman |
  |    2 | Susie         |   19 | woman |
  |    2 | Susie         |   18 | woman |
  +------+--------------+------+-------+
  3 rows in set (0.00 sec)
  

  　delete from student_data;清空表　

•  修改数据

• MySQL [Carrie]> update student_data set id=1 where id=2;
  Query OK, 2 rows affected (0.00 sec)
  Rows matched: 2  Changed: 2  Warnings: 0
  
  MySQL [Carrie]> select * from student_data;
  +------+--------------+------+-------+
  | id   | name_student | age  | sex   |
  +------+--------------+------+-------+
  |    1 | Carrie       |   18 | woman |
  |    1 | Susie        |   19 | woman |
  |    1 | Susie        |   18 | woman |
  +------+--------------+------+-------+
  3 rows in set (0.00 sec)
  

•  指定查看表中的数据

• MySQL [Carrie]> select * from student_data;
  +------+--------------+------+-------+
  | id   | name_student | age  | sex   |
  +------+--------------+------+-------+
  |    1 | Carrie       |   18 | woman |
  |    1 | Susie        |   19 | woman |
  |    1 | Susie        |   18 | woman |
  +------+--------------+------+-------+
  3 rows in set (0.00 sec)
  
  MySQL [Carrie]> select name_student from student_data where age=18;
  +--------------+
  | name_student |
  +--------------+
  | Carrie       |
  | Susie        |
  +--------------+
  2 rows in set (0.00 sec)
  

•  去除表中重复的信息

• MySQL [Carrie]> update student_data set name_student='Carrie' where age=18;
  Query OK, 1 row affected (0.00 sec)
  Rows matched: 2  Changed: 1  Warnings: 0
  
  MySQL [Carrie]> select * from student_data;
  +------+--------------+------+-------+
  | id   | name_student | age  | sex   |
  +------+--------------+------+-------+
  |    1 | Carrie       |   18 | woman |
  |    1 | Susie        |   19 | woman |
  |    1 | Carrie       |   18 | woman |
  +------+--------------+------+-------+
  3 rows in set (0.00 sec)
  
  MySQL [Carrie]> select distinct *from student_data;
  +------+--------------+------+-------+
  | id   | name_student | age  | sex   |
  +------+--------------+------+-------+
  |    1 | Carrie       |   18 | woman |
  |    1 | Susie        |   19 | woman |
  +------+--------------+------+-------+
  2 rows in set (0.00 sec)
  

•  给数据排序（默认升序排列，desc降序，asc升序，排序完成后，还可以加limit对数据进行限制，比如limit 2，3只显示2-3行）

• MySQL [Carrie]> select *from student_data order by age desc;
  +------+--------------+------+-------+
  | id   | name_student | age  | sex   |
  +------+--------------+------+-------+
  |    2 | Susie        |   19 | woman |
  |    1 | Carrie       |   18 | woman |
  |    1 | Carrie       |   18 | woman |
  +------+--------------+------+-------+
  3 rows in set (0.00 sec)
  

 15.聚合函数

常用的求最大，最小，平均数等聚合函数

函数名称	函数作用
MIN	查询指定列中的最小值
MAX	查询指定列中的最大值
COUNT	查询结果总行数统计
SUM	求和，返回指定列的总和
AVG	求平均数，返回指定列的平均值

为了后续实例中便于理解，先在 TEST 数据库中创建数据表 STUDENT，其表结构和表数据如下

select a.* from table a;

id	name	score
1	zhangsan	98
2	lisi	99
3	wangwu	100

1. min() 函数
   例：在 student 表中查询所有分数的最小值
   
   例：在 student 表中查询所有姓名的最小值
   
   注：min() 函数即可查找数值类型，也可用于字符类型；min() 函数可以判断字母大小，并返回最小的字符或字符串值，字符型数据比较时，按照ASCII码值大小进行比较，从a到z，a的ASCII码最小，z的ASCII码最大；
2. max() 函数
   例：在 student 表中查询所有分数的最大值
   
   例：在 student 表中查询所有姓名的最大值
   
   注：与min() 函数类似
3. count() 函数
   例：在 student 表中查询所有分数的列表总和
   
4. sum() 函数
   例：在 student 表中查询所有分数的总和
   
5. avg() 函数
   例：在 student 表中查询所有分数的平均值
   

 16.添加数据库中的用户

• MySQL [Carrie]> create user 'Carrie'@'licalhost' identified by '123123';
  Query OK, 0 rows affected (0.00 sec)
  
  MySQL [Carrie]> select user from mysql.user;
  +--------+
  | user   |
  +--------+
  | root   |
  | root   |
  | Carrie |
  |        |
  | root   |
  |        |
  | root   |
  +--------+
  7 rows in set (0.00 sec)
  

17.删除数据库中的用户

• MySQL [Carrie]> select user,host from mysql.user;
  +--------+---------------+
  | user   | host          |
  +--------+---------------+
  | root   | 127.0.0.1     |
  | abc    | 192.168.2.100 |
  | root   | ::1           |
  | Carrie | licalhost     |
  |        | localhost     |
  | root   | localhost     |
  |        | mysql         |
  | root   | mysql         |
  +--------+---------------+
  8 rows in set (0.00 sec)
  
  MySQL [Carrie]> drop user 'abc'@'192.168.2.100';
  Query OK, 0 rows affected (0.00 sec)
  
  MySQL [Carrie]> select user,host from mysql.user;
  +--------+-----------+
  | user   | host      |
  +--------+-----------+
  | root   | 127.0.0.1 |
  | root   | ::1       |
  | Carrie | licalhost |
  |        | localhost |
  | root   | localhost |
  |        | mysql     |
  | root   | mysql     |
  +--------+-----------+
  7 rows in set (0.00 sec)
  

18.给用户授权

• 　实例是给主机下的用户授权，如果是远程授权直接将localhost换成可以用的域名或者IP地址或者IP段进行授权。比如：

• grant all privileges on student_data to Carrie@'192.168.2.%' identified by '123123';

• grant all privileges on student_data to Carrie@'192.168.2.0/24' identified by '123123';

  MySQL [Carrie]> grant all privileges on student_data to Carrie@'localhost' identified by '123123';
                   授权    在student_data上的所有权限 给Carrie@'localhost' 确认其密码为123123
  Query OK, 0 rows affected (0.00 sec)
  
  MySQL [Carrie]> select user,host from mysql.user;
  +--------+-----------+
  | user   | host      |
  +--------+-----------+
  | root   | 127.0.0.1 |
  | root   | ::1       |
  | Carrie | licalhost |
  |        | localhost |
  | Carrie | localhost |
  | root   | localhost |
  |        | mysql     |
  | root   | mysql     |
  +--------+-----------+
  8 rows in set (0.00 sec)
  
  MySQL [Carrie]> show grants for Carrie@localhost;
  +---------------------------------------------------------------------------------------------------------------+
  | Grants for Carrie@localhost                                                                                   |
  +---------------------------------------------------------------------------------------------------------------+
  | GRANT USAGE ON *.* TO 'Carrie'@'localhost' IDENTIFIED BY PASSWORD '*E56A114692FE0DE073F9A1DD68A00EEB9703F3F1' |
  | GRANT ALL PRIVILEGES ON `Carrie`.`student_data` TO 'Carrie'@'localhost'                                       |
  +---------------------------------------------------------------------------------------------------------------+
  2 rows in set (0.00 sec)

           一般all privileges 都会有哪些权限给用户呢？如下图：

                                        

19.刷新权限　 

• MySQL [Carrie]> flush privileges;
  Query OK, 0 rows affected (0.00 sec)
  

20.撤回权限

          用revoke权限将用户权限收回

• MySQL [Carrie]> revoke select on  student_data from Carrie@'localhost';
  Query OK, 0 rows affected (0.00 sec)
  
  MySQL [Carrie]> flush privileges;
  Query OK, 0 rows affected (0.00 sec)
  
  MySQL [Carrie]> show grants for Carrie@localhost;
  +----------------------------------------------------------------------------------------------------------------------------------------------------------+
  | Grants for Carrie@localhost                                                                                                                              |
  +----------------------------------------------------------------------------------------------------------------------------------------------------------+
  | GRANT USAGE ON *.* TO 'Carrie'@'localhost' IDENTIFIED BY PASSWORD '*E56A114692FE0DE073F9A1DD68A00EEB9703F3F1'                                            |
  | GRANT INSERT, UPDATE, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER, CREATE VIEW, SHOW VIEW, TRIGGER ON `Carrie`.`student_data` TO 'Carrie'@'localhost' |
  +----------------------------------------------------------------------------------------------------------------------------------------------------------+
  2 rows in set (0.00 sec)
  

21.数据备份操作

• 　mysqldump是逻辑备份，将数据以执行语句的形式备份出来到/Carrie的文件中，-B后加 数据库
• 　　

  [root@mysql ~]# mysqldump -uroot -p123123 -B Carrie >> /Carrie;