finds on child models

i've looking for the sql to do a comparison of objects in a model's
has_many objects. specifically it's a simple model:

class Person
   has_many :things

class Things
   belongs_to: person

i can save the person and their 3 (or however many) things. now i
just need a way to search their 3 things against all other people's 3
things to see if they're the same. for instance.

@person.thing 1 = 'baseball'
@person.thing 2 = 'tire'
@person.thing 3 = 'shovel'

what's the sql (and it it possible with #find to return a collection
of people with the same things that the person searching using 3 text
fields has?