基于MYSQL中的另一个表值更新表列
假设我有两张桌子: 第一个是产品:基于MYSQL中的另一个表值更新表列,mysql,sum,Mysql,Sum,假设我有两张桌子: 第一个是产品: +------------------+-----------------+--------+ | Product Name | Type | Price | +------------------+-----------------+--------+ | Carrots | Vegetables | 10 | | Oranges | Fruits |
+------------------+-----------------+--------+
| Product Name | Type | Price |
+------------------+-----------------+--------+
| Carrots | Vegetables | 10 |
| Oranges | Fruits | 20 |
| Beer | Drinks | 50 |
| Milk | Dairy products | 30 |
| Burgers | meat | 40 |
| Baguettes | bread | 10 |
+-----------+---------+-----------+-------------+
| Item1 | Item2 | Item3 | TotalPrice |
+-----------+---------+-----------+-------------+
| Carrots | Oranges | Beer | |
| Milk | Burgers | Baguettes | |
+-----------+---------+-----------+-------------+
第二个是组合:
+------------------+-----------------+--------+
| Product Name | Type | Price |
+------------------+-----------------+--------+
| Carrots | Vegetables | 10 |
| Oranges | Fruits | 20 |
| Beer | Drinks | 50 |
| Milk | Dairy products | 30 |
| Burgers | meat | 40 |
| Baguettes | bread | 10 |
+-----------+---------+-----------+-------------+
| Item1 | Item2 | Item3 | TotalPrice |
+-----------+---------+-----------+-------------+
| Carrots | Oranges | Beer | |
| Milk | Burgers | Baguettes | |
+-----------+---------+-----------+-------------+
我想根据每个组合产品的总价格更新其总价格
例如,牛奶、汉堡和法式面包组合的“总价格”栏将为80
如何实现这一点?您可以使用子查询根据组合项计算总和:
UPDATE combos SET total_price = (SELECT SUM(price) FROM products
WHERE product_name IN (item1, item2, item3));
您的方法不太正确,关系没有正确表示。考虑两个实体
产品
和组合
,以及它们之间的关系。一个组合
当然可以有很多产品
,对吗?但是,一个产品
可以属于许多组合
,同意吗?这意味着两者之间的关系是多对多。要对这种关系进行建模,您需要第三个表,Combo\u Product
,只有当Product
属于Combo
时,该表才会包含一条记录
使用此模型,您可以简单地使用brige表将两者连接起来,并执行聚合以获得任意和
查询将按以下行进行:
select c.id_combo, sum(p.price)
from combo c
join combo_product cp on c.id_combo = cp.id_combo
join product p on cp.id_product = p.id_product
group by c.id_combo;