I tried the first SQL Quiz question. It's supposed to be an easy one and I wrote the query based on my submitted SQL files. However, when I clicked check button, it told me my answer was wrong and corresponding error message was "no such column: StartDate". However, I did use StartDate as an attribute in my schema. So right now I'm confused whether we should use our own work or some provied schema. And where can I find the provided schema? Thank you.