Group by Count of DateTime Per Hour by removing Duplicates?

I have a table named loginData:

userName timestamp
abc      '2007-01-01 12:00:12 AM'
def      '2021-01-01 12:09:12 AM'
abc      '2021-01-01 12:40:12 AM'
abcde    '2021-01-01 12:44:12 AM'

From this table I want to query the data in such a way that It doesn’t count duplicates. I want to get data like this:

userLoggedIN - 3

Considering abc has logged in twice to count it as one. How to do this?

Answer

You can use count(distinct):

select count(distinct userName)
from loginData;