The Sunnah is not to greet when asking a question.

The Shaykh : And what remains for us is that you greeted, and likewise the brother before you greeted when asking the question. This is not in accordance with the Sunnah, because the Companions (may Allah be pleased with them), when they wanted to ask the Messenger of Allah (peace and blessings be upon him) a question, they did not greet him, except for one who came to the gathering, in which case he would greet.