Question

我有两张表，其中包含提供信息和其他包含产品的信息像这样的东西：

           OFFER                                 PRODUCTS
ID      Number      Version          poID      offer_id     Product       how_many
==========================            ========================================
1          123       1                1         1              Apple        1
2          123       2                2         1              Banana       2
3          124       1                3         1              Orange       1
                                      4         2              Apple        1
                                      5         2              Banana       2
                                      6         2              Orange       2
                                      7         2              Kiwi         1
                                      8         3              Apple        2
                                      9         3              Banana       3

我想列出目前提供的产品数量。由于OFFER（id = 2）是（id = 1）的更新，因此只应计算（id = 2）。

我该如何最好地查询？

Answer 1

首先，您需要获得所有最新的优惠：

select o.id
from offer o
where version = (select max(version)
                 from offer o2
                 where o2.number = o.number);

基于以上所述，您可以获得所有产品：

select p.*
from products p
where offer_id in (select o.id
                   from offer o
                   where version = (select max(version)
                                    from offer o2
                                    where o2.number = o.number));

Answer 2

SELECT * 
FROM products
WHERE offer_id = (SELECT MAX(id) FROM offer)

或者，如果您更喜欢连接语法

SELECT p.* 
FROM products p
INNER JOIN (SELECT MAX(id) id FROM offer) o ON p.offer_id = o.id

编辑（仍然不完全确定这是你想要的，而不会看到你想要的结果）

SELECT p.* 
FROM products p
INNER JOIN offer o on p.offer_id = o.id
INNER JOIN 
(SELECT number, max(version) 
 FROM offer
 GROUP BY number
) oMax ON o.number = oMax.number AND o.version = oMax.version

Answer 3

如果id和version相关：

select sum(how_many) from products p
join offer on p.offer_id=offer.id
join (
    select number, max(version) version from offer group by number  
) x 
on offer.id=x.id and offer.version = x.version

Answer 4

试试这个：

select [list columns here]
from products p
join (select offernumber, max(id) as ID from offer group by offernumber) a
    on a.id = p.offer_id

如果您需要提供除要约编号和ID以外的其他列：

select [list columns here]
from products p
join (select offernumber, max(id) as ID from offer group by offernumber) a
    on a.id = p.offer_id
join offer o on o.id = a.id

使用SQL连接仅选择最新版本的数据

4 个答案: