在Rails中联接不相关的表

Question

Bottom line - I want to join two database tables together that do not "belong to" each other but do have a common field.

After some research on StackOverflow, I found some solutions to similar problems that use SQL directly, like so:

Address.joins('INNER JOIN phones on addresses.person_id = phones.person_id').select("addresses.*, phones.*").limit(1)

When I use the above statement in my rails console, however, it performs the following SQL query:

Address Load (0.3ms)  SELECT  addresses.*, phones.* FROM `addresses` INNER JOIN phones on addresses.person_id = phones.person_id LIMIT 1

and returns the following data (censored for privacy reasons):

=> #<ActiveRecord::Relation [#<Address id: 0001, created_at: "YYYY-MM-DD hh:mm:ss", updated_at: "YYYY-MM-DD hh:mm:ss", description: nil, line1: "123 Evergreen Terrace", line2: "", line3: "", city: "Springfield", state: "IL", country: "USA", zip: "11111", building_number: "001", person_id: 1, address_type: "Home", primary: false, show: nil, job_id: nil, room_number: "001", source: "HR", effective_date: "YYYY-MM-DD">]>

Not a single field from the Phone table made it into the final record.

Do I have to make these unrelated tables "belong to" each other to make them work? Like -

class Address < ActiveRecord::Base
  belongs_to :person
end

class Phone < ActiveRecord::Base
  belongs_to :person
  belongs_to :address
end

Or can I do what I want without modifying my models' relationships?

Answer 1

The data might not be visible in the query, but the record will respond to those fields that were fetched by the query, meaining if the phone record has a number attribute for example, doing a call to .number will respond with the fetched number

address = Address.joins(....).select('*').first
address.number  # => this will print the phone number of the phone record.