mysql服务启动报错Redirecting to systemctl start mysqld.serviceFailed to start mysqld.service:Unit not found.

输入service mysqld start报错

报这个错多半是没有安装成功在yum install mysql-community-server的时候报错

The GPG keys listed for the "MySQL 5.7 Community Server" repository are already installed but they are not correct for this package.
Check that the correct key URLs are configured for this repository.

解决方案：
先执行如下命令

rpm --import https://repo.mysql.com/RPM-GPG-KEY-mysql-2022

再执行安装命令
yum install mysql-community-server
最后再次service mysqld start