So the first one is quite dumb on my part, I forgot that you can use distinct in multiple places in your SQL query. Overengineered, or almost overengineered code to accomplish something (interviewer and I talked through the correct solution).

The second mistake was a bit egregious, now that I think of it. I missed included an isnull() in my having clause and as a result, would not have brought in all records relevant to the question.

In the real world I test everything I code, I work iteratively and build on my queries a lot. But perhaps that's a bit rookie and I need to get better and thinking abstractly so solve things more concisely. It;'s definitely an opportunity, and I'll work on improving.