Should I answer the question which is the exact duplicate of another question, and it is mentioned as duplicate in comment?
How can we stop people answering such questions, if we should stop people doing it?
I sometimes do. I just did on another MSO question in fact.
The most important thing to do is to either vote to close as a duplicate (if you have the rep) or flag as a duplicate and comment, so that others know it's a duplicate and it will eventually get closed.
If you feel like answering and have something useful to say , you can answer it. But keep in mind it's probably going to be closed (and maybe deleted after that) so you're kinda wasting your time.
You won't be able to stop people from asking duplicate questions, best you can do is get good at closing them quickly :-)
You shouldn't answer such a question.
If you have the reputation to close as duplicate, do so (this will automatically add a comment if there are no current comments on the question).
If you do not have the reputation, add a comment with a link to the duplicate.
You can't stop people from answering the question, but bringing attention to the duplicate will help.
It depends. A question is not a duplicate until the community decides it's one, one user posting a comment is not enough. That may take some time, and the OP may even revise the question in a way that's not a duplicate. Even if the question is closed, it's always possible to be revised & re-opened.
For the specific scenario you are describing, if you agree that the question is a duplicate:
- Flag it as such,
- Post your answer in the original question, if you feel it will add new & substantial information.
This is one of the few issues with which I agree with Jeff Atwood. Unless the question is trivial:
How to cast a double to decimal in C#
then having a more-or-less duplicate question, that's a bit different, maybe with a slightly different title, whose answer will be different than those posted to the potential duplicates is good for the community. It provides one more path for Google to direct future developers who are stuck.
If the question is intelligent, then answer it. Your time will be much more productively spent providing help to the user than searching for a duplicate question to close with.
If it's an exact duplicate, leave a comment with a link of the duplicate for the user to visit, and flag the question appropriately.
If it's a vague duplicat (contains the same content of another question, yet could be considered to be somewhat different) then I would leave an answer only if the possible duplicate doesn't already contain an answer that correctly answers the new question.
Say question 1 is similar to question 2 to where some say it is a duplicate, but question 2 doesn't have any answers that could answer question 1. I beleive in this scenario it would be appropriate to answer the question. Also, even if the question is an exact duplicate of the original, but the original does not have a clear answer, you should include a new answer on the new question (or the old one for that matter...)