CODEWITHSUNDEEP
ruby-on-railsactiverecord
user1466717
user1466717

Reputation: 789

Optimize ActiveRecord query

I have 2 tables in database: cars and domains. One car can have many domains and one domain can have many cars.

In my project three models:

class Car < ActiveRecord::Base

  has_many :cars_domains
  has_many :domains, :through => :cars_domains

...

class Domain < ActiveRecord::Base

    has_many :cars_domains
    has_many :cars, :through => :cars_domains
...

class CarsDomain < ActiveRecord::Base
  belongs_to :car
  belongs_to :domain
end

I want to see cars which without domain:

@cars = Car.find(:all, :conditions => ['id not in(select car_id from cars_domains where domain_id = ?)', params[:domain_id]])

It's work, but I think it's very difficult. Maybe possible to do it more simple?

Upvotes: 1

Views: 269

Answers (1)

agmcleod
agmcleod

Reputation: 13621

Tried this in a quick app I created:

domain = Domain.find(params[:domain_id])
Car.includes(:cars_domain).where('cars_domain.domain_id <> ?', domain.id)

The reason I query the domain object is because I'm always weary about passing a value from the request headers as a query parameter in SQL.

Upvotes: 1

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