Rails 中的多列主键

发布于 2024-12-17 05:40:26 字数 411 浏览 0 评论 0原文

我正在尝试将桌面应用程序迁移到rails（还处理相当老式的现有数据库）。问题是我在一列中没有唯一的 ID，但表的三列保证了记录的唯一性。

鉴于我有三个表：

authors
  author_name,
  author_letter,
  author_nr1,
  author_nr2
  ...

titles
  titel_nr,
  titel_name,
  ...

author_titles
  titel_nr,
  author_letter,
  author_nr1,
  author_nr2

作者的“主键”由author_letter、author_nr1、author_nr2组成。

那么我是否需要在这里使用多列主键才能使 Rails 关联正常工作？或者我在这里走错了方向？

原文

I'm trying to migrate a desktop application to rails (also dealing with quite old fashioned existing database). The problem is that I don't have a unique ID in one column, but it's three columns of a table that guarantee uniqueness of a record.

Given I have three tables:

authors
  author_name,
  author_letter,
  author_nr1,
  author_nr2
  ...

titles
  titel_nr,
  titel_name,
  ...

author_titles
  titel_nr,
  author_letter,
  author_nr1,
  author_nr2

The "primary key" of authors consists of author_letter, author_nr1, author_nr2 here.

So do I need sort of a multicolumn primary key here to have rails associations working? Or am I going in the wrong direction here?

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巨坚强 2024-12-24 05:40:26

不。主键是（像 Rails 默认的那样）记录的 ID。

此外，您可以设置唯一的键，例如

    add_index :users, [:merchant_id, :email], unique: true
    add_index :users, [:merchant_id, :login], unique: true

“This”，以保护您的数据库。为了捕捉 Rails 中的独特性，您需要在模型中写入：

  validates_uniqueness_of :email,    scope: :merchant_id
  validates_uniqueness_of :login,    scope: :merchant_id

No. The Primary Key is (like rails default) the ID of the Record.

In addition you can set unique Keys like

    add_index :users, [:merchant_id, :email], unique: true
    add_index :users, [:merchant_id, :login], unique: true

This potects your database. To catch the uniqueness in Rails you need to write into your model:

  validates_uniqueness_of :email,    scope: :merchant_id
  validates_uniqueness_of :login,    scope: :merchant_id

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罪歌 2024-12-24 05:40:26

存在一个名为 composite_primary_keys 的 gem，它允许使用多个列构建主键。

所以，是的，您可以使用多列主键。

但是，如果您能够更改数据模型（情况并非总是如此），我建议向每个表添加一个列 ID，因为这将使您的生活更轻松（并且性能也更高）。

[编辑]

您的composite_primary_keys 类定义将如下所示

class Author
  set_primary_keys :author_letter, :author_nr1, :author_nr2
  has_many :titles, :through => :author_title
end

class Title
  set_primary_key :title_nr
end

class AuthorTitle
  belongs_to :title, :foreign_key => :title_nr
  belongs_to :authori, :foreign_key => [:author_letter, :author_nr1, :author_nr2]
end

希望这会有所帮助。

There exists a gem called composite_primary_keys that will allow to build a primary key using multiple columns.

So, yes, you can use multicolumn primary key.

But, if you are able to change the datamodel (which is not always the case), I would propose to add a column ID to each table, as this will make your life easier (and is also much more performant).

[EDIT]

Your class definition with composite_primary_keys will look like this

class Author
  set_primary_keys :author_letter, :author_nr1, :author_nr2
  has_many :titles, :through => :author_title
end

class Title
  set_primary_key :title_nr
end

class AuthorTitle
  belongs_to :title, :foreign_key => :title_nr
  belongs_to :authori, :foreign_key => [:author_letter, :author_nr1, :author_nr2]
end

Hope this helps.

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