sudo apt-get autoremove --purge mysql-server-5.7 
#sudo apt-get remove mysql-server         # 没用到,已经没有mysql-server
#sudo apt-get autoremove mysql-server  # 没用到,已经没有mysql-server
sudo apt-get remove mysql-common
sudo rm -rf /etc/mysql/  /var/lib/mysql    #很重要
#清理残留数据
dpkg -l |grep ^rc|awk ‘{print $2}‘ |sudo xargs dpkg -P  
sudo apt autoremove
sudo apt autoreclean

sudo apt-get install mysql-server
sudo apt-get install mysql-client
sudo apt-get install libmysqlclient-dev