前言：最近自己的服务器重装了系统，上面的软件都没了，重装了MySQL5.7，但是遇到了许多问题，要么就是下载的是MySQL8.0要么就是mysql-community-server下载失败，经过几个小时的google终于安装上了，并且能够在本机的navicat(sqlyog)能够访问到服务器上的数据库。于是写了这篇详细的文档，给以后的自己以及遇到相同问题的朋友一个好的参考方案。

1. 卸载MySQL

安装之前先把服务器上关于MySQL的资源全部卸载，防止遇到不知名的错误(此方法同样适用于想卸载MySQL的)

1.1 yum方式查询是否安装了MySQL

yum list installed mysql*

如果出现：

Dependencies resolved.
===============================================================================================================================================================================================
 Package                                              Architecture                         Version                                       Repository                                       Size
===============================================================================================================================================================================================
Installing:
 mysql-community-server                               x86_64                               5.7.29-1.el7                                  mysql57-community                               175 M
Installing dependencies:
 mysql-community-client                               x86_64                               5.7.29-1.el7                                  mysql57-community                                26 M
 mysql-community-common                               x86_64                               5.7.29-1.el7                                  mysql57-community                               311 k
 mysql-community-libs                                 x86_64                               5.7.29-1.el7                                  mysql57-community                               2.5 M

Transaction Summary

说明有，需要卸载。

1.2 yum方式卸载（如果有，则执行这一步）

1. yum remove mysql-community-server mysql-community-client mysql-community-common mysql-community-libs
2. rm -rf /var/lib/mysql
3. rm /etc/my.cnf

1.3 rpm查看是否安装mysql

rpm -qa | grep -i mysql

如果出现

mysql-community-client-5.7.27-1.el6.x86_64
mysql-community-common-5.7.29-1.el7.x86_64
mysql-community-server-5.7.29-1.el7.x86_64
mysql-community-libs-5.7.27-1.el6.x86_64

则说明存在

1.4 rpm卸载MySQL

rpm -e mysql-community-client-5.7.27-1.el6.x86_64
rpm -e mysql-community-common-5.7.29-1.el7.x86_64
rpm -emysql-community-server-5.7.29-1.el7.x86_64
rpm -e mysql-community-libs-5.7.27-1.el6.x86_64
cd /var/lib/  
rm -rf mysql/

1.5 清除剩余资源文件:

whereis mysql
出现：mysql: /usr/bin/mysql /usr/lib64/mysql /usr/share/mysql /usr/share/man/man1/mysql.1.gz
删除：rm -rf "上面的资源文件(如：/usr/bin/mysql)"

1.6 删除MySQL残留的配置文件

rm –rf /usr/my.cnf
rm -rf /root/.mysql_sercret

1.7 再次检查是否完全删除
```
chkconfig --list | grep -i mysql
chkconfig --del mysqld
```
如果还有资源没有删除干净，重复以上方法

2. 安装MySQL

2.1 添加MySQL存储库

禁用MySQL默认的AppStream存储库：

sudo dnf remove @mysql
sudo dnf module reset mysql && sudo dnf module disable mysql

centos8没有MySQL存储库，因此我们将使用centos 7存储库。创建一个新的存储库文件。
```
sudo vim /etc/yum.repos.d/mysql-community.repo
```

将以下数据插入上面的存储库中

[mysql57-community]
name=MySQL 5.7 Community Server
baseurl=http://repo.mysql.com/yum/mysql-5.7-community/el/7/$basearch/
enabled=1
gpgcheck=0

[mysql-connectors-community]
name=MySQL Connectors Community
baseurl=http://repo.mysql.com/yum/mysql-connectors-community/el/7/$basearch/
enabled=1
gpgcheck=0

[mysql-tools-community]
name=MySQL Tools Community
baseurl=http://repo.mysql.com/yum/mysql-tools-community/el/7/$basearch/
enabled=1
gpgcheck=0

2.2 安装MySQL(这里我选择MySQL5.7)

sudo dnf --enablerepo=mysql57-community install mysql-community-server

2.2.1 如果安装失败,使用以下方法进行安装

先下载rpm包

wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-community-common-5.7.27-1.el6.x86_64.rpm
wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-community-libs-5.7.27-1.el6.x86_64.rpm
wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-community-client-5.7.27-1.el6.x86_64.rpm
wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-community-server-5.7.27-1.el6.x86_64.rpm

再安装

yum install -y mysql-community-common-5.7.27-1.el6.x86_64.rpm
yum install -y mysql-community-libs-5.7.27-1.el6.x86_64.rpm
yum install -y mysql-community-client-5.7.27-1.el6.x86_64.rpm
yum install -y mysql-community-server-5.7.27-1.el6.x86_64.rpm

2.3 下载完成后检查版本

 [root@aliyun-zuojun ~]# rpm -qi mysql-community-server 
 Name        : mysql-community-server
 Version     : 5.7.29
 Release     : 1.el7
 Architecture: x86_64
 Install Date: Sat 22 Feb 2020 11:04:07 AM CST
 Group       : Applications/Databases
 Size        : 801919839
 License     : Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved. Under GPLv2 license as shown in the Description field.
 Signature   : DSA/SHA1, Thu 19 Dec 2019 04:12:40 PM CST, Key ID 8c718d3b5072e1f5
 Source RPM  : mysql-community-5.7.29-1.el7.src.rpm
 Build Date  : Wed 18 Dec 2019 09:31:48 PM CST
 Build Host  : loki02.no.oracle.com
 Relocations : (not relocatable)
 Packager    : MySQL Release Engineering <mysql-build@oss.oracle.com>
 Vendor      : Oracle and/or its affiliates
 URL         : http://www.mysql.com/
 Summary     : A very fast and reliable SQL database server

出现以上信息说明安装成功

2.4 检查 mysql 源是否安装成功

yum repolist enabled | grep "mysql.*-community.*"
出现以下信息说明安装成功：
mysql-connectors-community MySQL Connectors Community                       141
mysql-tools-community      MySQL Tools Community                            105
mysql57-community          MySQL 5.7 Community Server

2.5 启动MySQL
```
 systemctl start mysqld
```

2.6 查看启动状态

systemctl status mysqld
// 出现以下信息，则启动成功
 Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: active (running) since Sat 2020-02-22 11:14:47 CST; 2h 19min ago
     Docs: man:mysqld(8)
           http://dev.mysql.com/doc/refman/en/using-systemd.html
  Process: 21345 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
  Process: 21323 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
 Main PID: 21349 (mysqld)
    Tasks: 30 (limit: 11516)
   Memory: 209.1M
   CGroup: /system.slice/mysqld.service
           ?..21349 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid

2.7 设置开机启动
```
systemctl enable mysqld
```
2.8 刷新所有修改过的配置文件
```
systemctl daemon-reload
```

2.9 获取安装mysql后生成的临时密码，用于登录

grep 'temporary password' /var/log/mysqld.log
# 如果出现如下列信息，密码为: BL=azx(1u;Br
2020-02-22T03:05:17.741049Z 1 [Note] A temporary password is generated for root@localhost: BL=azx(1u;Br

2.10 登录MySQL

mysql -uroot -p
# 再输入上面查找得到的临时密码即可进入mysql

2.11 修改登录密码

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass4!（修改后的密码，注意必须包含大小写字母数字以及特殊字符并且长度不能少于8位,否则会报错）';
或者通过：mysql> set password for 'root'@'localhost'=password('MyNewPass4!');
或者通过：mysql> use mysql;
        mysql> update user set password=PASSWORD('MyNewPass5!') where user='root';
        mysql> flush privileges;

2.12 添加远程登录用户(即本机访问服务器上的MySQL)

mysql> GRANT ALL PRIVILEGES ON *.* TO 'zhangsan（用户名）'@'%' IDENTIFIED BY 'Zhangsan2018!（密码）' WITH GRANT OPTION;
# 或者直接将root权限修改为可以通过远程访问(但不推荐)
mysql> use mysql;
mysql> UPDATE user SET Host='%' WHERE User='root';
mysql> flush privileges;

2.13 设置默认编码为utf-8（mysql安装后默认不支持中文）

vim /etc/my.cnf
# 进入文件后添加下面的配置即可
[mysqld]
character-set-server=utf8
[client]
default-character-set=utf8
[mysql]
default-character-set=utf8

2.14 重启MySQL服务并进入MySQL

shell> systemctl restart mysqld
shell> mysql -uroot -p
mysql> show variables like 'character%';

出现如下则说明编码修改完成

+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8                       |
| character_set_connection | utf8                       |
| character_set_database   | utf8                       |
| character_set_filesystem | binary                     |
| character_set_results    | utf8                       |
| character_set_server     | utf8                       |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+

退出MySQL

mysql> quit

使用本机电脑navicat/sqlyog等一系列客户端工具连接服务器上的mysql，用户名和密码为远程用户的用户名和密码，如果是将root权限修改为可以远程访问，就用root访问。

以上就是全部对mysql的安装与卸载的教程，希望对你有帮助。

可以参考mysql官网文档：https://dev.mysql.com/doc/refman/5.7/en/linux-installation-yum-repo.html