小编sms*_*are的帖子

这是我的数据库。FoodItems 只是普通表，但我想使用虚拟列来生成所有相关数据，例如 Servings.kcal 等于相关 (FieldItem.kcal*unit)/100（数据以每 100g/100ml 的千卡为单位指定）：

CREATE TABLE IF NOT EXISTS `DietDB`.`Servings` (
      `id` INT UNSIGNED NOT NULL,
      `FoodItem_id` INT UNSIGNED NOT NULL,
      `name` VARCHAR(255) NOT NULL,
      `units` DOUBLE UNSIGNED NULL,
      `kcal` INT GENERATED ALWAYS AS (SELECT (FoodItems.kcal*units)/100 FROM Servings JOIN FoodItems ON Servings.FoodItem_id = FoodItems.id) VIRTUAL,
      `carbohydrate` DOUBLE UNSIGNED NULL,
      `carbohydrate_sugar` DOUBLE UNSIGNED NULL,
      `fat` DOUBLE UNSIGNED NULL,
      `fat_saturated` DOUBLE UNSIGNED NULL,
      `fat_trans` DOUBLE UNSIGNED NULL,
      `protein` DOUBLE UNSIGNED NULL,
      `fibre` DOUBLE UNSIGNED NULL,
      PRIMARY KEY (`id`, `FoodItem_id`), …