whoisgregg - 4:30 pm on Apr 10, 2012 (gmt 0)
The query cache will not work if any part of the SELECT is non-deterministic. So, if you use a function like RAND() in your select expression, then that query will never be cached:
SELECT *, RAND() AS cache_buster FROM ...
This shouldn't have a dramatic affect on your overall execution time, nor should it throw off MySQL's other built-in optimizations. Since you can see that the value is changing on each reload, it gives you the confidence that you are not hitting the cache.