使用MINUS时在SQL中缺少右括号

Question

我得到一个＆＃34;缺少右括号＆＃34;以下代码的错误消息;我不明白为什么。

select region_name, avg(population) as atlagos_lakossag
from world_regions, countries 
where world_regions.region_id = countries.region_id group by region_name
minus
select region_name, min(lol) as atlagos_lakossag 
from 
(select region_name, avg(population) as lol from countries, world_regions 
where world_regions.region_id = countries.region_id group by region_name);