How to use DISTINCT and ORDER BY in same SELECT statement?

After executing the following statement:

SELECT  Category  FROM MonitoringJob ORDER BY CreationDate DESC

I am getting the following values from the database:

test3
test3
bildung
test4
test3
test2
test1

but I want the duplicates removed, like this:

bildung
test4
test3
test2
test1

I tried to use DISTINCT but it doesn't work with ORDER BY in one statement. Please help.

Important:

1. I tried it with:

   SELECT DISTINCT Category FROM MonitoringJob ORDER BY CreationDate DESC
   

   it doesn't work.

2. Order by CreationDate is very important.