You probable installed MySQL with a help of article like this — https://phoenixnap.com/kb/how-to-install-mysql-on-centos-7
So your mysql is controlled by systemctl.
Check current status —
sudo systemctl status mysqld.
Start service —
sudo systemctl start mysqld
Logs for systemctl are here — sudo journalctl -xe
Logs for mysql can be found here — /var/log/mysqld.log.
Configs are here — /etc/my.cnf.