使用 MySQL：以大写形式显示所有 Column_Name，按字母顺序排序，不重复

Question

我已经完成了这个问题，除了我需要我的查询不显示重复项。我该怎么做：

SELECT UPPER(surname) 
FROM customers
ORDER BY surname;

Answer 1

SELECT DISTINCT(UPPER(surname))
FROM customers
ORDER BY surname;

Answer 2

SELECT DISTINCT UPPER(surname) 
FROM customers
ORDER BY surname;

Using MySQL: Display all of the Column_Name in upper case, sorted alphabetically without duplicates