yum install mysql5.7

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

异常情况：

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