This came about while trying to construct an ActiveRecord query.
via http://stackoverflow.com/a/9540911/111363
Note that merge combines WHERE clauses using AND. While ActiveRecord does not currently have the ability to combine relations using OR instead, it is coming in ActiveRecord 5 (https://github.com/rails/rails/commit/9e42cf019f2417473e7dcbfcb885709fa2709f89).
It'll look something like this:
via http://tombroomfield.com/the-upcoming-active-record-or-method-will-clean-up-your-queries/