如何獲取產品以及每次購買的數量與一個SQL查詢？

Question

Buy有一個外鍵product_id。

所以除了SELECT * FROM products;我們有興趣得到每個產品的購買數量。

Answer 1

加入

SELECT Products.*, COUNT(Buy.ID) AS Bought 
FROM products 
    LEFT OUTER JOIN Buy ON products.ID = Buy.product_id 
GROUP BY Buy.product_id 

子查詢

SELECT 
    Products.*, 
    (SELECT COUNT(ID) FROM Buy WHERE product_id = Products.ID) AS Bought 
FROM products 

Answer 2

SELECT p.*,COUNT(b.product_id) FROM products p 
INNER JOIN buy b ON p.id=b.product_id 
GROUP BY b.product_id 

這就是我所能提供的所有信息。如果上述不起作用，兩者的表格結構都會有幫助。

Answer 3

線沿線的東西：

SELECT p.*, COUNT(buy.product_id) FROM product p INNER JOIN buy ON buy.product_id = p.id GROUP BY buy.product_id 

應該做的伎倆。