The whole process was really slow. But the interviewers are really nice. The SQL question is about window function. And the case is used to test your logic, business acumen.

They started with an online test followed by a video interview. Then moved on to the final onsite. This is by far the worst company I have ever seen. They conduct interviews because the employees get paid for it. They choose candidates internally and the results do not depend on how well you perform. Please do not waste your time interviewing for Wayfair.