Sqlite3,维基百科中的练习：

两个相连的表格

Manufactures: code, name

products: code, name, price, manufacturer 

//黄色是关联。

15. Select the name and price of the cheapest product.

??  ：使用嵌套结构，这样能得到所有最便宜的价格的产品，产品价格如果有相同的话。 

        如果只是写子结构内的代码，只能返回一行。 

SELECT Name, Price
FROM Products
WHERE Price = (SELECT MIN(Price) FROM Products);

16. Select the name of each manufacturer along with the name and price of its most expensive product.不是非常理解；

   SELECT A.Name, A.Price, F.Name
   FROM Products A INNER JOIN Manufacturers F
   ON A.Manufacturer = F.Code
     AND A.Price =
     (
       SELECT MAX(A.Price)
         FROM Products A
         WHERE A.Manufacturer = F.Code
     );