uninstall mysql ubuntu 18.04

$ sudo apt-get remove --purge mysql-server mysql-client mysql-common -y
$ sudo apt-get autoremove -y
$ sudo apt-get autoclean

rm -rf /etc/mysql
# Delete all MySQL files on your server:
sudo find / -iname 'mysql*' -exec rm -rf {} \;

$ sudo apt-get remove --purge mysql-server mysql-client mysql-common -y
$ sudo apt-get autoremove -y
$ sudo apt-get autoclean
$ sudo rm -rf /etc/mysql
# Delete all MySQL files on your server: 
$ sudo find / -iname 'mysql*' -exec rm -rf {} \;

sudo apt-get remove --purge mysql*

sudo service mysql stop  #or mysqld
sudo killall -9 mysql
sudo killall -9 mysqld
sudo apt-get remove --purge mysql-server mysql-client mysql-common
sudo apt-get autoremove
sudo apt-get autoclean
sudo deluser -f mysql
sudo rm -rf /var/lib/mysql
sudo apt-get purge mysql-server-core-5.7
sudo apt-get purge mysql-client-core-5.7
sudo rm -rf /var/log/mysql
sudo rm -rf /etc/mysql

mysql installation process