$ cat sql/getRecipeCost.sql
DROP PROCEDURE IF EXISTS getRecipeCost;
DELIMITER //
CREATE PROCEDURE getRecipeCost(id INT(10) unsigned, OUT cost DECIMAL(6,3) unsigned)
BEGIN
  DECLARE done INT DEFAULT 0;
  DECLARE ingredientSku MEDIUMINT(8) unsigned;
  DECLARE ingredientQty DECIMAL(8,2) unsigned;
  DECLARE ingredientCost DECIMAL(6,3);
  DECLARE ingredientRecipeId INT(10) unsigned;
  DECLARE myCursor CURSOR FOR
    SELECT sku,qty FROM recipes_data WHERE recipeid=id;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;

  IF ISNULL(cost) THEN
    SET cost=0;
  END IF;
  OPEN myCursor;
  myLoop: LOOP
    FETCH myCursor INTO ingredientSku,ingredientQty;
    IF done=1 THEN LEAVE myLoop; END IF;

    SELECT recipe_cost FROM vendors_products WHERE sku=ingredientSku
      INTO ingredientCost;
    IF ingredientCost=0 THEN
      SELECT recipeid FROM recipes WHERE sku=ingredientSku
        INTO ingredientRecipeId;
      call getRecipeCost(ingredientRecipeId, cost);
    ELSEIF ingredientCost != 0 THEN
      SET cost = cost + ingredientCost;
    END IF;
  END LOOP myLoop;
  SELECT cost;
END;
//
DELIMITER ;