I'm beginning to think that we need some kind of "posting shorthand" for replying to QotD.
My first suggestion: we need a term that means "I thought this looked straightforward, but I know that these questions are usually designed to trip us up, so I spent 15 minutes looking it over/thinking about it/querying/reviewing BoL/performing divination by entrails before deciding I was just going to answer the way I thought it should be answered. I was right, and I was surprised so many others got it wrong."
Maybe IKIWAR (pron. Icky-War, short for "I Knew I WAs Right"? 😉
Rob, maybe this would help your staff to understand their error: add another row to the table with a DATE of 2013-07-13 (i.e., not the MAX(Date)) and an Exchange_Rate of 0.11999 (i.e., the MAX(Exchange_Rate)) and ask them what this query would return:
SELECT Max(Exchange_Rate), Max(Date) FROM Currency
(Note the reversed ordering of the columns in the SELECT statement, which of course doesn't change the results.)
Would they then have expected to see some kind of grouping on Exchange_Rate?
Thanks for the question and for the explanation as to why it was an appropriate question,