in my opinion, "Maybe you should study some tutorials first", is slightly disrespectful, but made up for by posting a helpful link. I might suggest rephrasing something like, "after reviewing your code, it looks like you are missing some fundamentals on DCL use, here is a good resource: (link)"
(really wordy rephrasing - and I didn't review the code as my DCL skills are lacking)
but - in my opinion the OP should also learn to not take offense at minor issues, if you are frustrated, draft your response but then sit on it for a day or few hours before posting. Focus on the positive, example someone taking the time to share a post, ignore what you perceive as small petty stuff. Focusing on the negative won't get you more help.
lastly I recognize that roy_043 posts helpful responses all the time and I don't recall any one being rude, so I assume no offense was intended