I am curious how Forms creates the database queries for lookup rules. Does it combine all of the Lookup Rules for a form that has the same source and table/view or does it execute each one individually?

I became curious about this because of the way the Forms Layout Designer creates a new Lookup Rule each time when you create them from the field itself instead of combining them with other rules. I want to know from an efficiency point of view if I should be creating them one way or the other.