select 
a.area_code, b.group_full_name area_name, 
a.zone_code, b2.group_full_name zone_name,
a.region_code,b3.group_full_name region_name
from a 
left join b b1 on a.area_code = b1.group_id  
left  join b b2 on a.zone_code = b2.group_id  
left  join b b3 on a.region_code = b3.group_id;