SELECT child_2.id, child_2.sales,child_2.country,
         child_2.commission,child_2.agent_name,
         child_2.created_date,child_2.created_user,
         child_2.modified_user,child_2.modified_date,
         child1.agent_name, parent.agent_name, parent.working_area
FROM child_2
   LEFT JOIN
     child1
         ON child_2.country = child1.country
   LEFT JOIN
     parent
         ON child1.country = parent.working_area