Question

class Category < ActiveRecord::Base
  has_many :articles
end

class Article < ActiveRecord::Base
  belongs_to :category
  has_many :comments
  has_many :tags
end

导轨中的

Category.joins(:articles)等效

SELECT categories.* FROM categories
  INNER JOIN articles ON articles.category_id = categories.id

如果我想拥有rails-code，则等效于sql

SELECT * FROM categories
  INNER JOIN articles ON articles.category_id = categories.id

我该怎么办？

Answer 1

Category.select('*').joins(:articles)

或

categoyes = Category.select('*').includes(:articles)

和

categoyes.each do |category|
    puts category.articles
end

Answer 2

尝试使用select方法

categories = Category.select('*').joins(:articles)
categories.first.some_column_from_articles

Answer 3

我使用这种方法

Category.connection.select_all("SELECT * FROM categories
  INNER JOIN articles ON articles.category_id = categories.id").to_a

所有列都在rails上的ruby中加入

3 个答案: