I have a file geodatabase that is storing a number of important features for my project. When I add a feature to an ArcMap document and run Select by attribute (either from the tools or from the toolbar) over many of the fields, I get more features selected than I should. For example, if there is a field called ID with the values A, B, C, D and I select ID="A", I may get "A" and "B" returned as selected. I am running a New Selection, so that isn't the cause of the problem. The files I am working with are quite large- over 160,000 features. Any ideas?