Tableau Software QA Engineer interview questions

I had a technical phone interview, then a 4 hour in office interview, then a 1 hour interview with some upper management. Phone interview was pretty typical. I was asked some general/basic blackbox testing questions. The 4 hour in person interview was a bit more technical, since I have some coding experience they asked me to write a function that would take a random array of ints and see if 2 of the ints sum was equal to another value passed in (i.e. public bool findSum(int[] array, int sum)). The person asking this question definately wanted me to be considering performance. I answered this question well in my opinion. The last interview with the VP's didnt go so great they asked me a couple of tough questions that i didnt have great answers for (i.e. if i was testing a piece of software that lived on top of a DB what extra test cases i would come up with for different languages). I came up with tests for every new character (FYI the chinese alphabet has 1000's of characters) and a few other tests but i definately think they were looking for something specific that i didnt come up with.