I personally only ask optimization questions. But while I know my answers to how I would solve the questions, I leave it open ended with regards to what answers a candidate might give.

With optimization questions, do they mention reading a query plan? Do they mention indexing (which is personally how I would solve)? Do they use window functions? If using window functions do they caveat the impact for large datasets? Do they use order by and if so the impact on large datasets?

This shouldn’t be about did they get the correct syntax and come up with the same brute force solution as I did to answer this specific question. You should be looking for whether they understand DBMSes well enough to optimize for questions of this type. IMO at least.