Install MySQL 5.6 in Ubuntu 16.04
Ubuntu 16.04 only provides packages for MySQL 5.7 which has a range of backwards compatibility issues with code written against older MySQL versions.
Oracle maintains a list of official APT repositories for MySQL 5.6, but those repositories do not yet support Ubuntu 16.04. However, the 15.10 repos will work for 16.04.
Uninstall existing mysql 5.7 if any
sudo apt remove mysql-client mysql-server libmysqlclient-dev mysql-common
Check you removed everything
sudo dpkg -l | grep mysql
Purge remainders (e.g. marked with rc) with
sudo dpkg -P <package> [<package> ...].
Download the apt_config-debian package from Oracle and install it using from https://dev.mysql.com/get/mysql-apt-config_0.8.0-1_all.deb
sudo dpkg -i mysql-apt-config_0.8.0-1_all.deb
Choose "MySQL 5.6" and "Ubuntu Wily" (assuming Xenial is not yet provided)
Run
sudo apt-cache policy mysql-server
If this shows a 5.6 version, continue.
If not, check your /etc/apt/sources.list.d/mysql.list. It should look roughly like this:
### THIS FILE IS AUTOMATICALLY CONFIGURED ###
# You may comment out entries below, but any other modifications may be lost.
# Use command 'dpkg-reconfigure mysql-apt-config' as root for modifications.
deb http://repo.mysql.com/apt/ubuntu/ wily mysql-apt-config
deb http://repo.mysql.com/apt/ubuntu/ wily mysql-5.6
deb http://repo.mysql.com/apt//ubuntu/ wily mysql-tools
deb-src http://repo.mysql.com/apt/ubuntu/ wily mysql-5.6
You might have to replace "xenial" with "wily". Although you are using 16.04 (codename Xenial), Oracle currently seems to only provide 5.6 in the repos for 14.04 (codename Wiley). But those sources work for 16.04, too.
Create a file /etc/apt/preferences.d/mysql with this content
Package: *
Pin: origin "repo.mysql.com"
Pin-Priority: 999
Run
sudo apt-get update
Now recipe's run should provide
sudo apt install mysql-client-5.6 mysql-server-5.6 libmysqlclient-dev
You should get 5.6 versions.
In order to start the service and then schedule it to automatically load during boot
sudo systemctl start mysql && sudo systemctl enable mysql