2 indexes. Need to determine if particular field's value shows up in index 1 (index 2 is used as the list of value to search index 1 for)

Do I need to do some fancy joined search here? I have values that will show in index 2, and I want to check index 1 to see if they exist, then table results. Is this something that I need to provide a lot more information on? (i.e.: Log examples) At least some guidance would be helpful. :) Thanks!