Question

I am using Rails v2.3.2.

I have a model called UsersCar:

class UsersCar < ActiveRecord::Base
  belongs_to :car
  belongs_to :user
end

This model mapped to a database table users_cars, which only contains two columns : user_id, car_id.

I would like to use Rails way to count the number of car_id where user_id=3. I konw in plain SQL query I can achieve this by:

SELECT COUNT(*) FROM users_cars WHERE user_id=3;

Now, I would like to get it by Rails way, I know I can do:

UsersCar.count()

but how can I put the ...where user_id=3 clause in Rails way?

Answer 1

According to the Ruby on Rails Guides, you can pass conditions to the count() method. For example:

UsersCar.count(:conditions => ["user_id = ?", 3])

will generates:

SELECT count(*) AS count_all FROM users_cars WHERE (user_id = 3)