选择具有相同项目名称的行并显示最低价格

Question

我们有两个表格，布局如下：

Products
ID | Item | Supplier
1 | Harry Potter | Warner
2 | Harry Potter | Warner
3 | Game of Thrones | HBO
4 | The Simpsons | Warner
5 | The Simpsons | Warner

与

Prices
ID | Price
1 | 10.99
2 | 20.00
3 | 20.00
4 | 10.00
5 | 12.00

我正在尝试获取价格最低的商品的 ID，其中有两个商品具有相同的名称和供应商。

我可以得到有重复的行：

SELECT
Products.ID,Products.Item,Products.Supplier,Prices.price
FROM
Products
LEFT JOIN Prices ON Prices.ID = Products.ID
WHERE Products.ID IN (
SELECT ID FROM Products WHERE Supplier="Warner" GROUP BY Item HAVING count(*) > 1
)

然后如何修改它以仅显示价格最低的重复项目名称的 Products.ID ？

我尝试了 ORDER BY，但这对我来说是一个错误。

结果应该是：

ID | Item | Supplier | Price
1 | Harry Potter | Warner | 10.99
4 | The Simpsons | Warner | 10.00

谢谢，

瑞克

Answer 1

首先，如果您在 Products 表中将 ID 作为主键，则必须改进表的实现，您的数据将如下所示（您需要一个主键）。

Products
ID | Item | Supplier
1 | Harry Potter | Warner
2 | Game of Thrones | HBO

Prices
ID | Price
1 | 10.99
1 | 20.00
2 | 20

现在为了选择最低价格的商品，请使用 min 函数

SELECT
Products.ID,Products.Item,Products.Supplier, MIN(Prices.price)
FROM
Products
LEFT JOIN Prices ON Prices.ID = Products.ID;

Answer 2

/* Oracle syntax  
with Products as  
(  
select 1 id, 'Harry Potter' item,  'Warner' supplier from dual union all  
select 2 id, 'Harry Potter' item,  'Warner' supplier from dual union all  
select 3, 'Game of Thrones', 'HBO' from dual union all  
select 4, 'the simpsons', 'Warner' from dual union all  
select 5, 'the simpsons', 'Warner' from dual  
),  
Prices as  
(  
select 1 id, 10.99 price from dual union all  
select 2, 20.00 from dual union all   
select 3, 20.00 from dual union all  
select 4, 10.00 from dual union all  
select 5, 12.00 from dual)  
*/  

select distinct p.id from Products p join Prices c  
on (p.id = c.id)   
where (p.item, p.supplier, c.price) in  
(select item, supplier, min(price) from Products p join Prices c on (p.id = c.id) group by item, supplier having count(item) > 1);

（如果多个产品具有相同的项目价值和价格，则此查询将显示两种产品）