sql oracle count lower/upper case

Question

I have usernames with upper and lower case: Example:

• kelly, KellY, KELLY, kELLy, max, james, James, Carl

how to count this values in order to have the amount (count) in this case should be: 4 and not 8

SELECT 
    username,
    COUNT(*)
FROM 
    usertable
GROUP BY 
   username

Answer 1

您可以使用LOWER将所有名称转换为相同的大小写，然后计算DISTINCT值：

 COUNT(DISTINCT LOWER(username))