CentOS7默认数据库是mariadb,需要先卸载系统自带的Mariadb
// 查询出来已安装的mariadb
rpm -qa | grep mariadb
// 卸载mariadb，文件名为上述命令查询出来的文件
rpm -e –nodeps mariadb-libs-5.5.64-1.el7.x86_64
方式一、rpm包安装（适合离线安装）
下载地址
https://dev.mysql.com/downloads/mysql
点击 “No thanks, just start my download.”下载
# 切换到含有rpm包的目录中
# 使用rpm -ivh命令依次安装
-rw-r–r– 1 root root 14668996 May 11 09:16 mysql-community-client-8.0.29-1.el7.x86_64.rpm
-rw-r–r– 1 root root 2574424 May 13 11:46 mysql-community-client-plugins-8.0.29-1.el7.x86_64.rpm
-rw-r–r– 1 root root 648680 May 11 09:16 mysql-community-common-8.0.29-1.el7.x86_64.rpm
-rw-r–r– 1 root root 1949700 May 11 09:16 mysql-community-devel-8.0.29-1.el7.x86_64.rpm
-rw-r–r– 1 root root 2216040 May 13 11:48 mysql-community-icu-data-files-8.0.29-1.el7.x86_64.rpm
-rw-r–r– 1 root root 1575404 May 11 09:16 mysql-community-libs-8.0.29-1.el7.x86_64.rpm
-rw-r–r– 1 root root 55984868 May 11 09:16 mysql-community-server-8.0.29-1.el7.x86_64.rpm
方式二：yum安装（适合在线安装，方便）
以CentOS7举例：
查看有没有安装包，一般情况下不带
yum list mysql*
先下载mysql的repo源，下载地址为： https://dev.mysql.com/downloads/repo/yum/
1.下载mysql的repo源
wget https://repo.mysql.com//mysql80-community-release-el7-3.noarch.rpm
2.安装mysql的repo源
rpm -ivh mysql80-community-release-el7-3.noarch.rpm
3.安装mysql
yum install mysql* -y