How to return null values from a joined table if the matching row is missing?
did you try outer join?

select sales_people.person_id, last_name, first_name, sales_region.Region_id, coalesce(trim(sales_region.name),'NULL')  AS 'Region Name' 
from sales_region 
right outer join sales_people_region on sales_people_region.region_id = sales_region.region_id
right outer join sales_people on sales_people_region.`person_id` = sales_people.person_id
group by  sales_region.region_id, sales_people.person_id
having sales_people.person_id &gt;= ''
order by sales_people.person_id, sales_region.region_id asc;


`