ok, seeing the data makes all the difference. Also, I think that your description of what you were looking for was not quite correct. What you want are all records with and amid ID of 3 and all records with and amid ID of 13, right? In other words, it is the AND of the two sets, not the AND of the two operators. In that case (no pun) you want to use the IN operator. The AND will always return 0 records because it is impossible for a single record to meet both of those criteria. What you really want is the result of the OR of the operators - any record that meets any of the conditions. That's what the IN operator is a shortcut for.
-reed