[Big Data] Install MySQL database in CentOS7 environment

1. Install mysql

CentOS7 comes with Mariadb, we need to delete the .

我们在Linux系统中，如果要使用关系型数据库的话，基本都是用的mysql。
而且以往7以下版本的centos系统都是默认的集成有mysql。
然而对于现在最新的centos7系统来说，已经不支持mysql数据库，它默认内部集成了mariaDB。
如果我们想要使用 mysql 的话，就要先将原来的mariaDB卸载掉，不然会引起冲突。

1.1 Delete the CentOS system's own database

1. Query the version of mariadb in CentOS7

   ·查询命令：rpm -qa|grep mariadb
   

   

2. Forcefully uninstall the installed mariadb

   ·卸载命令：rpm -e --nodeps mariadb-libs-5.5.56-2.el7.x86_64
   

   

1.2 Start to install mysql

准备工作：
	在/opt/source路径下新建一个mysql的文件夹
	/opt目录下：(如果没有下面两个文件夹，可自行放置对应的文件夹中，路径一定不要搞混！)
		# module 存放解压后的文件
		# source 存放压缩包

1. Download mysql (download to local first)

   【了解】
   也可以直接在Linux系统中执行以下命令进行下载（以下两条命令是最新版Mysql8.0版本的下载和解压命令）：
   ·下载（该命令是下载到当前目录下）：wget https://dev.mysql.com/get/Downloads/MySQL-8.0/mysql-8.0.13-1.el7.x86_64.rpm-bundle.tar
   ·解压（解压到当前目录下）：tar -xvf mysql-8.0.13-1.el7.x86_64.rpm-bundle.tar
   

   Tsinghua University mirror download mysql5.7 version (click here)
   search myql
   

   Enter downloads
   
   to find mysql5.7 version
   
   Find and download mysql-5.7.38-1.el7.x86_64.rpm-bundle.tar

2. Use Xftp in Xshell to upload the MySQL file to the /opt/source folder in CentOS7
   (if you don’t have Xshell, you can use the rz command to upload)
   
   

3. decompress

   ·在source路径下新建一个mysql文件夹（如果之前没有创建的话）：mkdir mysql
   ·然后将mysql-5.7.38-1.el7.x86_64.rpm-bundle.tar解压到新建的mysql文件夹中
   ·解压命令：tar xvf mysql-5.7.38-1.el7.x86_64.rpm-bundle.tar -C ./mysql
   

   
   Then move the mysql folder under /opt/source to the /opt/module folder:

   ·命令：mv mysql ../module
   

   

4. Install (enter the mysql folder)

   依次执行以下5个命令
   ·安装命令1：rpm -ivh mysql-community-common-5.7.38-1.el7.x86_64.rpm	
   ·安装命令2：rpm -ivh mysql-community-libs-5.7.38-1.el7.x86_64.rpm
   ·安装命令3：rpm -ivh mysql-community-libs-compat-5.7.38-1.el7.x86_64
   ·安装命令4：rpm -ivh mysql-community-client-5.7.38-1.el7.x86_64.rpm
   ·安装命令5：rpm -ivh mysql-community-server-5.7.38-1.el7.x86_64.rpm
   

   
   
   
   An error is reported when executing command 3:
   

   After going through Baidu, I found that just add --force --nodeps after the command, as follows:

5. Check whether mysql is installed successfully:

   ·查询命令：rpm -qa|grep mysql
   

   

1.3 Start the mysql service and set a password

1. start mysql service

   ·启动命令：systemctl start mysqld
   ·查看mysql启动状态：systemctl status mysqld
   ·查看服务：netstat -nltp
   

   ·Start mysql, and view mysql startup status

   ·View service
   

2. Log in

   ·查找初始密码：
   	grep "A temporary password" /var/log/mysqld.log
   ·登录mysql
   	mysql -uroot -p
   	输入初始密码：/+3wHq0ag>z>
   ·设置新密码：
   	ALTER USER 'root'@'localhost' IDENTIFIED BY 'MySQL_123';
   	新密码为：MySQL_123
   ·退出客户端：
   	exit
   ·重新登录：
   	mysql -uroot -pMySQL_123
   

   ·Find the initial password:
   ·Successful login:
   
   ·Set a new password:
   
   ·Exit the client:
   
   ·Re-login:
   

1.4 Authorize all external users to connect to MySQL (understand)

·命令：GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY 'MySQL_123' WITH GRANT OPTION;
·说明： grant 权限名（所有的权限用all）on 库名(*全部).表名(*全部) to '要授权的用户名'@'%'(%表示所有的IP，也可以只写一个IP) identified by "密码"；

·刷新：flush privileges;
·重启mysql服务即可
	systemctl restart mysqld

2. The client operates mysql

Common query operations

1. 查看所有数据库：show databases;
2.切换到mysql数据库：use mysql;
3.查看数据库中有哪些表：show tables;
4.查看use表的内容：select Host,User from user;
5.查看表结构：desc user;
6.修改user表中host等于localhost的行（只能进行本机连接不能用于外网访问mysql数据库）：
	update user set host='%' where host='localhost';

1. View all databases:

2. Switch to the mysql database:

3. Check which tables are in the database:

4. View the contents of the use table:

5. View the table structure:

·Delete the row in the user table where host is equal to %
mysql>delete from user where host='%';

Solve the problem of garbled Chinese characters

1. Modify the mysql configuration file, and change the encoding method to: UTF format (to solve the problem of garbled Chinese characters)

   ·执行以下命令：
   	vim /etc/my.cnf
   	修改内容如下：
   		[client]
   		default-character-set=utf8
   		[mysql]
   		 character-set-server=utf8
   		 collation-server=utf8_general_ci
   ·重启mysql数据库：
   	service mysqld restart
   

   Before modification:
   
   After modification:
   
   Restart the mysql database
   
   View the changes after modification

   ·进入mysql
   ·输入以下命令：
   	status
   

   

create operation

1. Create a student database

   ·进入mysql
   ·创建student数据库命令：create database student default charset 'utf8';
   ·删除数据库命令：drop database student;
   

   

2. create stu table

   ·进入student数据库：use student;
   ·创建stub表：create table if not exists stu(id int primary key auto_increment,name varchar(20),gender char(2)) default charset 'utf8';
   

   

3. Insert records into stu table

   ·向sut表插入记录：insert into stu(name,gender)values('张三','男'),('小李','女'),('王五','男');
   ·查询stu表中的记录：select * from stu;
   

   

4. query form

   ·查看students数据库中的表：show tables;