mySql选择上/下

Question

我试图从两个表中编写一个选择，其中包含字符串的字段只在一个表中是UpperCase但查询和子查询似乎不起作用：

这有效：

SELECT City, Country
FROM Cities INNER JOIN Countries USING(IdCountry)
WHERE LOWER(Cities.City) IN
(LOWER('NEW YORK'), LOWER('PARIS'), LOWER('LONDON'))

这也有效：

SELECT LOWER(location) FROM locations

这不起作用：

SELECT City, Country
FROM Cities INNER JOIN Countries USING(IdCountry)
WHERE LOWER(Cities.City) IN
(SELECT LOWER(location) FROM locations)

我不明白错误