title: Write a query to display the names of the department and the staff count in each department, if staff not exist display the count as 0
body: <p>Write a query to display the names of the department and the staff count in each department, if the staff does not exist display the count as 0. Give an alias to staff count as staff_count. Sort the result based on department name.</p>
  
  <p>This is what I tried.</p>
  
  <pre><code>select department_name,count(*) as staff_count
  from left join staff on department.department_id=staff.staff_id
  group by department_name order by department_name;
  </code></pre>
  
  <p>I think there is something missing in my code.</p>