世界数据库练习

Question

人口最接近欧洲人口中位数的欧洲城市？

我尝试使用此代码，但是我总是在子查询中的where条件中出错

Select city.name,city.population from city
join country
on city.countrycode=country.code and country.continent='europe'
where city.population<(
avg(country.population)
where country.continent='europe')
order by city.population desc;

Answer 1

Select city.name,city.population from city
join country
on city.countrycode=country.code and country.continent='europe'
where city.population < (select avg(country.population)
where country.continent='europe')
order by city.population desc;

Answer 2

好的，我找到了解决方案，我的错误是重复了where子句，同时我已经在连接中声明了它：

file1 = input("Enter the name of the first file: ")
file1_open = open(file1, encoding=guess_encoding(file1))
file1_content = file1_open.read()