MySQL学习笔记2018-02-07更新

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win10下安装

1. https://dev.mysql.com/downloads/mysql/下载并解压mysql-5.7.21-winx64.zip
2. 在 D:\mysql-5.7.21-winx64\目录中新建my.ini文件

[mysql]
# 设置mysql客户端默认字符集
default-character-set=utf8
[mysqld]
# 设置3306端口
port=3306
# 设置mysql的安装目录
basedir=D:\\software\mysql-5.7.21-winx64
# 设置mysql数据的存放目录
datadir=D:\\software\mysql-5.7.21-winx64\data
# 允许最大连接数
max_connections=200
# 服务端使用的字符集默认为8比特编码的latin1字符集
character-set-server=utf8
# 创建新表时将使用的默认存储引擎
default-storage-engine=INNODB

1. 以管理员身份运行C:\Windows\system32\cmd.exe
   
   切换到目录D:\mysql-5.7.21-winx64\bin
   
   生成mysql服务

D:\mysql-5.7.21-winx64\bin>mysqld -install
Service successfully installed.

生成data目录D:\mysql-5.7.21-winx64\bin>mysqld --initialize-insecure --user=mysql

启动mysql服务

D:\mysql-5.7.21-winx64\bin>net start mysql
MySQL 服务正在启动 .
MySQL 服务已经启动成功。

登录数据库(默认密码为空)D:\mysql-5.7.21-winx64\bin>mysql -uroot

修改密码

mysql> show databases; # mysql语句后面必须加分号
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

mysql> use mysql;
Database changed
mysql> update user set authentication_string=password("toor") where User="root";
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1
mysql>flush privileges;  # 刷新权限
mysql>exit
Bye

关闭mysql服务

D:\mysql-5.7.21-winx64\bin>net stop mysql
MySQL 服务正在停止.
MySQL 服务已成功停止。

Linux下安装

基本语法

• 增

# 创建数据库
mysql> create database tests charset utf8;
# 创建数据表
mysql> create table teacher(
    ->   id int auto_increment,
    ->   name char(32) not null default 'zhangsan',
    ->   age int not null,
    ->   register_date date not null,
    ->   primary key (id));
# 插入数据
mysql> insert into student (name,age,register_date,class) values("lema",22,"2018-02-02","201601"),
    ->("michael",12,"2018-02-01","201601");
# 增加一个字段classroom
mysql> alter table student add classroom int;

• 删

# 删除数据内容
mysql> delete from student where id=2;
# 删除字段
mysql> alter table student drop age;

• 查

mysql> show databases; # 显示mysql中所有数据库名称
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| test               |
+--------------------+
mysql> use test; # 使用test数据库作为当前数据库
Database changed
mysql> show tables; # 显示当前数据库下所有表
mysql> select * from student; # 显示student表中所有字段的具体内容
mysql> select * from student\G; # 将查询结果按列打印
*************************** 1. row ***************************
       stu_id: 1
         name: lema
register_date: 2018-02-06
*************************** 2. row ***************************
       stu_id: 2
         name: alex
register_date: 2018-02-06
# 获取数据表结构
mysql> show columns from student;
mysql> desc student;
+---------------+----------+------+-----+---------+----------------+
| Field         | Type     | Null | Key | Default | Extra          |
+---------------+----------+------+-----+---------+----------------+
| stu_id        | int(11)  | NO   | PRI | NULL    | auto_increment |
| name          | char(32) | NO   |     | NULL    |                |
| register_date | date     | NO   |     | NULL    |                |
+---------------+----------+------+-----+---------+----------------+
# 偏移量查询
mysql> select * from student limit 1;
+----+------+-----+---------------+-------+
| id | name | age | register_date | class |
+----+------+-----+---------------+-------+
|  1 | alex |  30 | 2018-02-07    |  NULL |
+----+------+-----+---------------+-------+
mysql> select * from student limit 1 offset 2;
+----+---------+-----+---------------+--------+
| id | name    | age | register_date | class  |
+----+---------+-----+---------------+--------+
|  3 | michael |  12 | 2018-02-01    | 201601 |
+----+---------+-----+---------------+--------+
# 模糊查询
mysql> select * from student where register_date like "2018-02%";
select * from student where id>3 and age<20;
select * from student where id>3 or age<20;

• 改

# 修改字段的数据内容
mysql> update student set register_date="2017-03-01" where id=3;
# 修改字段的数据类型
mysql> alter table student modify id int not null;
# 修改字段的名称和数据类型
mysql> alter table student change id stu_id int;

• 排序

# 按照第3个字段排序
mysql> select * from student order by 3;
+----+---------+---------------+--------+------+
| id | name    | register_date | class  | age  |
+----+---------+---------------+--------+------+
| 2  | lema    | 2017-01-01    | 201602 |   12 |
| 3  | michael | 2017-03-01    | 201601 |   31 |
| 1  | alex    | 2018-02-07    | 201602 |   31 |
| 4  | david   | 2018-03-03    | 201703 |   34 |
| 5  | mm      | 2018-09-02    | 201801 |   56 |
+----+---------+---------------+--------+------+
# 分组
mysql> select name,count(*) from student group by name;
mysql> select name,sum(age) from student group by name;

用户授权

• 用户权限管理主要有以下作用：
  
  1.限制用户访问哪些库哪些表
  
  2.限制用户对哪些表执行select,drop,alter,create等操作
  
  3.限制用户登录的IP和域名
  
  4.限制用户自己的权限是否可以授权给其它用户
• 新建用户

mysql> grant all privileges on *.* to 'lema'@'%' identified by 'toor' with grant option;
Query OK, 0 rows affected, 1 warning (0.52 sec)
mysql> flush privileges; # 刷新权限
Query OK, 0 rows affected (0.14 sec)

  # all privileges：将所有权限授予用户，也可以指定具体权限，如select,create等
  # *.*：应用到所有数据库所有表，数据库名.表名
  # 'lema'@'%'：'用户名'@'IP或域名'，%表示任意主机
  # identified by 'toor'：设置登录密码
  # with grant option：允许用户将自己的权限授予其它用户

• 查看用户权限&删除权限

mysql> show grants for "root"@"localhost";
+---------------------------------------------------------------------+
| Grants for root@localhost                                           |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION        |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)

mysql> revoke create on *.* from 'lema'@'localhost';
Query OK, 0 rows affected (0.00 sec)

• 查看所有用户&删除用户&用户重命名

mysql> select host,user from mysql.user;
+-----------+---------------+
| host      | user          |
+-----------+---------------+
| localhost | lema          |
| localhost | mysql.session |
| localhost | mysql.sys     |
| localhost | root          |
+-----------+---------------+
4 rows in set (0.00 sec)

mysql> drop user 'lema'@'localhost';
Query OK, 0 rows affected (0.00 sec)

mysql> rename user 'lemachin'@'localhost' to 'lema'@'localhost';
Query OK, 0 rows affected (0.00 sec)

• 修改密码

# 更新mysql.user表
mysql> update mysql.user set authentication_string=password('toor') where user='lema';

# 用set password命令
mysql> set password for 'lema'@'localhost' =password('toor');

# mysqladmin位于bin目录下
D:\mysql-5.7.21-winx64\bin>mysqladmin -ulema -proot password toor