how do I do when villain flops a set?

[mtagliaf]

I'm interested in knowing what my BB/100 is when I'm up against a set. It's probably pretty bad b/c the hand would have to get to showdown to see it (the DB won't know if I fold to a cbet on the flop when someone is holding a set). I will catch multiway pots that get to showdown even if I fold early, though.

Is there a way to filter on opponent's holdings? Or to write a query?

[WhiteRider]

You can do this in a custom report using a custom filter.
Create a report in the Holdem Cash Player Statistics section and leave Filter on Active Player enabled in the report filters.
Add the stats you want to see and add this as a custom filter:
holdem_hand_player_combinations.id_hand in (SELECT holdem_hand_player_combinations.id_hand from holdem_hand_player_combinations WHERE holdem_hand_player_combinations.flg_f_threeoak)
..will include only hands where someone has three of a kind on the flop. Unfortunately it includes your sets too (I can't see how to remove those at the moment) and doesn't limit to hands where you saw the flop but you can filter those out using Simple Filters.
Tutorial: Custom Reports and Statistics