如何從數據透視表拿到最後更新的價格在MYSQL

Question

下面是表模式

客戶

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

產品

------------------------------ 
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 

價格

------------------------------------------- 
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 

我想要得到的是通過用戶ID分類每個產品的最後價格的這一結果，像這樣

user_id product_id  last_price 
1  1    200    

這是1號（price_history行沒有產品的最新更新價格7）

這是我到目前爲止已經完成，它給了不正確的結果

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 

真正會感謝你的幫助！

謝謝！

Answer 1

你可以使用在爲得到最大的價格加入到你的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 
)