Recently I ran a command in mysql that resulted in this error:

mysql: [ERROR] unknown variable 'sql_mode=IGNORE_SPACE,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'

So I had to add a line to the mysql config file. In Ubuntu 16:

# nano /etc/mysql/mysql.conf.d/mysqld.cnf

Add the following line under mysqld

[mysqld]
sql_mode = "STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"

Restart mysql:

# systemctl restart mysql