With Elixir Ecto, how do I add a has_many relationship in a migration?

Question

I want to write something like this:

defmodule JobHunt.Repo.Migrations.CompaniesHaveManyJobs do
  use Ecto.Migration

  def change do
    alter table (:companies) do
      add :jobs, :has_many, Job
    end
  end
end

Running mix ecto.migrate with this migration gives an error, so what is the right way to do this?

Answer 1

Our you could use this way as the documentation recommends:

alter table(:jobs) do
  add :company_id, references(:companies)
end

I'm not sure whether the plural version is required here: references(:companies) but it did not work for me with phermacy (singular)

Answer 2

You should add the required foreign key to the jobs table:

defmodule JobHunt.Repo.Migrations.CompaniesHaveManyJobs do
  use Ecto.Migration

  def change do
    alter table(:jobs) do
      add :company_id, :integer
    end
  end
end