I keep getting an error message after trying to run query

Tried running a query using what was given in the video but keep getting an error 

select emp_no, from_date, to_date, count(emp_no) as NUM
from dept_emp
group by emp_no
having NUM > 1;

above is the code 

Error Code: 1055. Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'employees.dept_emp.from_date' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

here is the error I keep getting