CODEWITHSUNDEEP
ruby-on-railsactiverecord
Daniel Thompson
Daniel Thompson

Reputation: 2351

activerecord -- query many to many table for records from one of the tables (rather than just rows from the join table)

I spent a lot of time today trying to figure out how to query a many to many table for records from one of the tables it belongs to.

If I have a members table that joins users and events, what kind of query would find all of the users attending a given event, or all of the events that a given user is attending?

I ultimately came across something like this (which works): 

 User.joins(:members).where("members.event_id = ?", @event.id)

But can this kind of query be done without the SQL syntax? Something like:

Member.where(user: @user).first.events

Upvotes: 0

Views: 307

Answers (1)

lightalloy
lightalloy

Reputation: 1165

You should be able to access user's events and event's users like this:

@event.users
@user.events

if you define The has_many :through association (http://guides.rubyonrails.org/association_basics.html#the-has-many-through-association)

class User < ApplicationRecord
  has_many :members
  has_many :events, through: :members
end

class Member < ApplicationRecord
  belongs_to :user
  belongs_to :event
end

class Event < ApplicationRecord
  has_many :members
  has_many :users, through: :members
end

Upvotes: 1

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