sudo apt-get --purge remove mysql-client mysql-server mysql-common
sudo apt-get autoremove

Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
 linux-headers-3.2.0-31-virtual linux-headers-3.2.0-31
Use 'apt-get autoremove' to remove them.
The following packages will be REMOVED:
 libdbd-mysql-perl* libmysqlclient18* mysql-client* mysql-client-5.5* mysql-common* mysql-server*
 mysql-server-5.5*
0 upgraded, 0 newly installed, 7 to remove and 0 not upgraded.
After this operation, 67.5 MB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 105097 files and directories currently installed.)
Removing mysql-server ...
Removing mysql-server-5.5 ...
mysql stop/waiting
Purging configuration files for mysql-server-5.5 ...
Removing mysql-client ...
Removing mysql-client-5.5 ...
Removing libdbd-mysql-perl ...
Removing libmysqlclient18 ...
Purging configuration files for libmysqlclient18 ...
Removing mysql-common ...
Purging configuration files for mysql-common ...
dpkg: warning: while removing mysql-common, directory '/etc/mysql' not empty so not removed.
Processing triggers for ureadahead ...
Processing triggers for man-db ...
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place

sudo rm -rf /etc/mysql/