Delete_all在查找范围下与rails连接

Question

我有一个book模型，一个标签模型和一个名为bookstags的连接模型，它们看起来如下:

当我想要读取所有的via_tags时，Book.first。Via_tags它将工作，
但是当我尝试删除所有相关的via_tags时，我尝试了Book.first.via_tags.delete_all()我得到了一个Exception。

ActiveRecord::StatementInvalid: SQLite3::SQLException: near "INNER": syntax error: DELETE FROM "tags" INNER JOIN "books_tags" ON "tags".id = "books_tags".tag_id WHERE (("books_tags".book_id = 25)) AND ("tags"."kind" = 0)

所以我想问的是，是否有可能执行delete_all与连接?

class Book < ActiveRecord::Base
  has_many :tags, :through =>  :books_tags
end
class BooksTags < ActiveRecord::Base
  belongs_to :book
  belongs_to :tag
  def self.with_via_tag
    find(:all, :joins => :tag, :conditions => {:tags => {:kind => Tag.kind_index(:via)}})
  end
end
class Tags
  has_many :books_tags
  has_many :books, :through => :books_tags
  @kinds = [:via,:cate,:attr]
  def self.kind_index kind
    @kinds.index(kind)
  end
end

Answer 1

不存在，因为delete_all丢弃了连接信息。请参阅此答案，了解编写查询的另一种方式:https://stackoverflow.com/a/7639857/156109