wget https://repo.mysql.com/mysql80-community-release-el7-3.noarch.rpm
rpm -ivh mysql80-community-release-el7-3.noarch.rpm
yum repolist all | grep mysql
yum-config-manager --disable mysql80-community
yum-config-manager --enable mysql57-community
yum install mysql-community-server --nogpgcheck
yum -y install mysql-devel --nogpgcheck
systemctl restart mysqld.service
grep "temporary password" /var/log/mysqld.log
異常情況：
rpm -qa | grep mariadb
rpm -e --nodeps mariadb-connector-c-config-3.1.11-2.el8_3.noarch
rpm -e --nodeps mariadb-connector-c-3.1.11-2.el8_3.x86_64
https://blog.csdn.net/li_wen_jin/article/details/105140360