mobilizon/priv/repo/migrations/20180110094301_create_participants.exs

defmodule Mobilizon.Repo.Migrations.CreateParticipants do
  use Ecto.Migration

  def change do
    create table(:participants, primary_key: false) do
      add :role, :integer
      add :event_id, references(:events, on_delete: :nothing), primary_key: true
      add :account_id, references(:accounts, on_delete: :nothing), primary_key: true

      timestamps()
    end

    create index(:participants, [:event_id])
    create index(:participants, [:account_id])

  end
end