Elixir 当一个表的主键是一个关联的id时，如何做

我正在为freeradius mysql开发RESTAPI（所以我不管理数据库…） Freeradius有一个奇怪的模式：

“组”表：

“用户”表：

我的问题是我想做：

schema "radusergroup" do
  belongs_to :user, Rascal.User, foreign_key: :username, references: :username, type: :string, primary_key: true
  field :priority, :integer
  field :groupname, :string
end

但星外组织不允许。 有没有办法轻松地做这件事

---

谢谢

我已尝试实现您需要的结构

迁移 用户：

组：

defmodule ExampleApp.Repo.Migrations.CreateGroup do
  use Ecto.Migration

  def change do
    create table(:radusergroup) do

      add :username, references(:userinfo, on_delete: :nothing, column: :username, type: :string)

      add :priority, :integer
      add :groupname, :string

      timestamps
    end
    create index(:radusergroup, [:username])

  end
end

defmodule ExampleApp.Group do
  use ExampleApp.Web, :model

  schema "radusergroup" do
    belongs_to :username, ExampleApp.Username, references: :username, type: :string

    field :priority, :integer
    field :groupname, :string

    timestamps
  end

  @required_fields ~w()
  @optional_fields ~w()

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, @required_fields, @optional_fields)
  end
end

模型 用户：

组：

defmodule ExampleApp.Repo.Migrations.CreateGroup do
  use Ecto.Migration

  def change do
    create table(:radusergroup) do

      add :username, references(:userinfo, on_delete: :nothing, column: :username, type: :string)

      add :priority, :integer
      add :groupname, :string

      timestamps
    end
    create index(:radusergroup, [:username])

  end
end

defmodule ExampleApp.Group do
  use ExampleApp.Web, :model

  schema "radusergroup" do
    belongs_to :username, ExampleApp.Username, references: :username, type: :string

    field :priority, :integer
    field :groupname, :string

    timestamps
  end

  @required_fields ~w()
  @optional_fields ~w()

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, @required_fields, @optional_fields)
  end
end

---

它符合您的需要吗？

请显示您的迁移。

defmodule ExampleApp.User do
  use ExampleApp.Web, :model

  @primary_key {:username, :string, autogenerate: false}
  schema "userinfo" do
    has_one :group, ExampleApp.Group, foreign_key: :username, on_delete: :delete_all

    timestamps
  end

  @required_fields ~w()
  @optional_fields ~w()

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, @required_fields, @optional_fields)
  end
end

defmodule ExampleApp.Group do
  use ExampleApp.Web, :model

  schema "radusergroup" do
    belongs_to :username, ExampleApp.Username, references: :username, type: :string

    field :priority, :integer
    field :groupname, :string

    timestamps
  end

  @required_fields ~w()
  @optional_fields ~w()

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, @required_fields, @optional_fields)
  end
end