Lost connection to MySQL server/DBMS connection is not available

Hi Eugene!
Thanks for reaching out.

You can try changing the DBMS connection read timeout interval (in seconds) setting in the SQL Editor tab in the Workbench's preferences. Change it to something like 180. Then restart the Workbench or reconnect to the DBMS and rerun the query.

Hope this helps.
Best,
Tsvetelin

Hi Tsvetelin Tsonkov,
Thank you for your response. However, after changing the DBMS connection read timeout interval to 180, I was able to perform only two queries and then the error again. 

select
e.gender, d.dept_name, round(avg(s.salary),2) as salary, year(s.from_date) as calendar_year
from
t_salaries s
join
    t_employees e ON s.emp_no = e.emp_no
join
t_dept_emp de ON de.emp_no = e.emp_no
join
t_departments d ON d.dept_no = de.dept_no
group by d.dept_no, e.gender, calendar_year
having calendar_year <= 2002
order by d.dept_no;