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

The problem is that the columns used in the ORDER BY aren’t specified in the DISTINCT. To do this, you need to use an aggregate function to sort on, and use a GROUP BY to make the DISTINCT work.

Try something like this:

SELECT DISTINCT Category, MAX(CreationDate) 
FROM MonitoringJob 
GROUP BY Category 
ORDER BY MAX(CreationDate) DESC, Category