DBIO.scala

  /**
   *  Update both the number of sold units for a product and total income for a supplier
   *  Not the best written function WRT missing records, but let's not complicate things ;)
   */
  def sellProduct(name: String): DBIO[BigDecimal] = {
    val productQuery = products.filter(_.name === name)
    for {
      (_, supplierId, _, price, unitsSold) <- productQuery.result.map(_.head)
      supplierIncomeQuery = suppliers.filter(_.id === supplierId).map(_.income)
      income <- supplierIncomeQuery.result.map(_.head)
      updatedIncome = income + price
      _ <- supplierIncomeQuery.update(updatedIncome)
      _ <- productQuery.map(_.unitsSold).update(unitsSold + 1)
    } yield updatedIncome
  }