问题1:
select
continent
,avg(gdp) 平均gdp
from world
where (gdp > 20000000000
and population > 60000000)
or (gdp <8000000000
and capital like '%a%a%a%')
group by continent
having sum(population) >= 300000000
order by count(name) desc
limit 1
不是说group by后只能select已有的量,或者加聚合的量嘛
为什么这个函数还可以select population呢?
问题2:
请问sql语句中的“like”和“=”有什么区别呀?