I was asked a similar question in an interview. The problem I used was a time out issue on our Finance system after upgrading from SQL Server 2000 to SQL Server 2005. I showed what I had done to try and solve the problem but also tried to show how I worked with the application team to solve the problem and how the problem was finally solved. The solution was to index a table that had no index. Identifying the index became a team effort as the SQL tools alone didn't find it.

Showed the interviewer my process from a SQL Server side, and that I was team player working with the app team as well to finally solve the problem.

From what you said, I am impressed.