Has_many通过查询

Question

我有 2 个模型（书籍和作者）和第三个 table 加入他们（has_many 通过关联）。

我正在尝试在我的应用程序中实现搜索，并且运行对两个 table 进行查询。我的查询看起来像这样，但我无法找出问题所在：

Book.includes(:authors, :author_books).where("books.title LIKE ? OR authors.name = LIKE ?", "%#{book}%", "%#{book}%")

这是我运行得到的错误：

PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "authors"
SELECT "books".* FROM "books" WHERE (books.title LIKE '%Harry%' OR authors.name = LIKE '%Harry%')

这是我对三个 table 的架构：

create_table "author_books", force: :cascade do |t|
    t.bigint "author_id"
    t.bigint "book_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["author_id"], name: "index_author_books_on_author_id"
    t.index ["book_id"], name: "index_author_books_on_book_id"
  end

  create_table "authors", force: :cascade do |t|
    t.string "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  create_table "books", force: :cascade do |t|
    t.string "title"
    t.text "description"
    t.string "image"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer "rating"
    t.string "critics"
    t.float "price"
  end

author_book.rb

class AuthorBook < ApplicationRecord
  validates_presence_of :author, :book
  belongs_to :author
  belongs_to :book
end

author.rb

class Author < ApplicationRecord
  validates :name, uniqueness: true
  has_many :author_book
  has_many :books, through: :author_book
end

book.rb

class Book < ApplicationRecord
  validates :title, uniqueness: true, :case_sensitive => false
  has_many :author_book
  has_many :authors, through: :author_book
  has_many :categories, through: :category_book

  def self.search_book(book)
    if book
      Book.joins(:authors, :author_books).includes(:authors, :author_books).where("books.title LIKE ? OR authors.name = LIKE ?", "%#{book}%", "%#{book}%")
    end
  end  
end

我在我的图书控制器中这样调用这个 search_book 方法：

def search
    @books = Book.search_book(params[:book])
end

有什么帮助吗？谢谢！

Answer 1

您忘记加入作者和 author_books 您的关系。 includes 同时加载 :author 和 :author_books 但在不同的查询中。

试试这个：

Book.joins(:authors, :author_books).includes(:authors, :author_books).where("books.title LIKE ? OR authors.name = LIKE ?", "%#{book}%", "%#{book}%")

Answer 2

来自docs

If you want to add conditions to your included models you’ll have to explicitly reference them.

也就是说，您需要像下面那样将 references(:authors) 添加到您的查询中以解决错误

Book.includes(:authors, :author_books).where("books.title LIKE ? OR authors.name = LIKE ?", "%#{book}%", "%#{book}%").references(:authors)

更新：

Can't join 'Book' to association named 'author_books'; perhaps you misspelled it?

您应该将 has_many :author_book 替换为 has_many :author_books，将 through: :author_book 替换为 through: :author_books

Has_many通过查询

Has_many through query

ruby-on-rails

model-associations