$ 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 purge mysql-server*

#Use 
sudo apt-get -f install 
# to fix your missing dependencies, then execute 
sudo apt-get remove mssql-server 
#to uninstall the server.