mysql - 根据 MYSQL 中的另一个表值更新表列

Question

假设我有 2 个表:

第一个是产品:

+------------------+-----------------+--------+
| Product Name     |      Type       | Price  |
+------------------+-----------------+--------+
| Carrots          | Vegetables      | 10     |
| Oranges          | Fruits          |     20 |
| Beer             | Drinks          |     50 |
| Milk             |  Dairy products |     30 |
| Burgers          |  meat           |     40 |
| Baguettes        | bread           |    10  |

第二个是组合:

+-----------+---------+-----------+-------------+
| Item1     |  Item2  |   Item3   |  TotalPrice |
+-----------+---------+-----------+-------------+
| Carrots   | Oranges | Beer      |             |
| Milk      | Burgers | Baguettes |             |
+-----------+---------+-----------+-------------+

我想根据其产品的总价更新每个组合的总价。

例如，牛奶、汉堡和长棍面包组合的“总价”列将为 80。

我怎样才能做到这一点？

Answer 1

您可以使用子查询根据组合的项目计算总和:

UPDATE combos SET total_price = (SELECT SUM(price) FROM products
    WHERE product_name IN (item1, item2, item3));