如何从MYSQL中的数据透视表中获取最后更新的价格

Question

以下是表架构

客户

------------------------------
id  name
------------------------------
1   joe
4   jane

产品

------------------------------
id  title 
------------------------------
1   iphone  
2   ipad

customers_products

------------------------------
id  product_id  customer_id
------------------------------
1   1       1   
2   2       1
3   1       5
4   1       9

价格

-------------------------------------------
id  product_id  price   created_at 
-------------------------------------------
3   1       300         2017-04-01
4   2       450         2017-04-01
5   2       500         2017-04-02
6   1       320         2017-04-04
7   1       200         2017-04-05

我想要获得的是每个按用户ID分类的产品的最终价格结果，如此

user_id product_id       last_price
1       1                200            

产品编号1的最后更新价格（price_history row no 7）

这是我到目前为止所做的，并且结果不正确

select 
id,prices.price as current_price,customers_products as price
from prices
join products on products.id = prices.product_id
join customers_products on customers_products.product_id = prices.product_id
where customers_products.customer_id = 1
group by prices.product_id order by prices.id desc 

真的很感谢你的帮助！。

谢谢！

Answer 1

您可以在其中使用元组获取最大价格加入您的customers_products

select  customers_products.customer_id , customers_products.product_id, prices.price as last_price
from customers_products
inner join prices on prices.product_id = customers_products
where ( created_at ,product_id) in (
    select max(created_at ), product_id  
    from price 
    group product_id
)