I disagree with your assessment of that question, it is not a trivial select statement if you read the question carefully. The fact that your answer didn't match the question is kind of indicative.
Easy questions are fine as long as they are good. (I pretty much only answer easy questions, since I'm no expert at anything.)
Why error come when click plz halp
=> questions should be closed.
I've tried this and that, got this specific error message here, from this exact code block, and I can't figure out where I'm wrong. Can someone explain why the frob doesn't budge in this case?
=> question shows effort, and (probably) has merit, even if it's completely obvious to someone with a bit of domain knowledge why the frob is stuck.
Answer it if you know the answer. Provide as much information as necessary to give the appropriate clues if it looks like homework.
You can also (sometimes) try and make the question more general and searchable by editing it.
Closing as exact duplicate is also often possible with "easy" questions. Find a good, canonical question/answer pair and vote to close/flag as a dup. If you can't find a good, helpful duplicate, answer and make your answer become that great, helpful reference for all the future noobs that will inevitably stumble into this issue.
Now a lot of "easy" questions are, even with your best effort at making them more general, too localized. I personally have (almost) no qualms at both answering helpfully and voting to close as too localized. (Not the zero-effort-by-asker questions though, those get downvotes and close votes more often then not, no answer.)