From terminal execute the following statements:
sudo apt purge mariadb-*;
sudo apt purge mysql-*;
sudo rm -r /usr/share/mysql/;
rm -r /etc/mysql/;
sudo rm -r /lib/systemd/system/mysql.service;
sudo apt install mysql-server
From terminal execute the following statements:
sudo apt purge mariadb-*;
sudo apt purge mysql-*;
sudo rm -r /usr/share/mysql/;
rm -r /etc/mysql/;
sudo rm -r /lib/systemd/system/mysql.service;
sudo apt install mysql-server