Centos7 executes the command service mysqld start and prompts Failed to start mysqld.service: Unit mysqld.service not loaded

An error condition
After mysql is installed on Centos7, service Mysqld Start cannot be started and Service Mysqld Stop cannot be stopped
The solution
find/-name mysql.server
The following path is found
/usr/share/mysql/mysql.server
so
/usr/share/mysql/mysql.server start
It can start successfully
Use the/usr/share/mysql/mysql. Server stop
You can close it successfully