Boolean search is not conceptually simple, Nielsen Norman Group has some great reports on web search UX that suggest advanced search is where any parameters like AND/OR belong. The optional logic is really for more advanced users with a more advanced job to be done.
This question about intuitive interfaces for composing Boolean logic illustrates what I mean. All the most well-received examples are elegant and appropriately complex to match the conceptual complexity. They don’t try to simplify what is not really that simple.
“Show overlapping results” doesn’t sound familiar to me. Will your users know what that means? A checkbox is a simple enough form control but if the label defies instant comprehension, not sure what you gain.
My point is that anything beyond a text field and a search button qualifies as “Advanced.”
That said, I think I’ve seen a few decent examples of advanced search in practice. In a previous gig, I did a lot of social media research on forums. I found that the modest search form gave me just enough to:
- Scope my searches within a certain time frame
- Specify “all” or “any” for search terms in the query
- Format my results for brevity
I used that search feature again and again to successfully dig up really specific topics of discussion, and I never really found myself longing for Boolean operators.
Everyone is different. Do what’s best for your users based on careful study of their needs, but my suggestion is if you want to keep it simple try to avoid exposing AND/OR altogether.