blockscout/apps/explorer/priv/repo/migrations/20180717204948_create_balances.exs

defmodule Explorer.Repo.Migrations.CreateBalances do
  use Ecto.Migration

  def change do
    create table(:balances, primary_key: false) do
      add(:address_hash, references(:addresses, column: :hash, type: :bytea), null: false)
      add(:block_number, :bigint, null: false)
      add(:value, :numeric, precision: 100, null: false)

      timestamps(null: false, type: :utc_datetime)
    end

    create(unique_index(:balances, [:address_hash, :block_number]))
  end
end