Oracle 进行一对一连接

Question

我想从多对多进行一对多连接。两个表样本：

制作：

ORDER	PRODUCED_AMOUNT	PRODUCT_ID
Order1	1000	ProductID1
Order1	1000	ProductID1
Order1	5000	ProductID2

订单：

ORDER	AMOUNT_TO_PRODUCE	PRODUCT	PRODUCT_ID
Order1	600	Product1 - note1	ProductID1
Order1	600	Product1 - note2	ProductID1
Order1	600	Product1 - note3	ProductID1
Order1	5000	Product2	ProductID2

如果我写一个像这样的示例查询

SELECT ORDERS.ORDER, ORDER.AMOUNT_TO_PRODUCE, SUM(PRODUCTION.PRODUCED_AMOUNT), ORDERS.PRODUCT
FROM ORDERS JOIN PRODUCTION ON ORDERS.PRODUCT_ID = PRODUCTION.PRODUCT_ID
GROUP BY ORDERS.ORDER, ORDER.AMOUNT_TO_PRODUCE, ORDERS.PRODUCT

我明白了

ORDER	AMOUNT_TO_PRODUCE	PRODUCED_AMOUNT	PRODUCT
Order1	600	2000	Product1 - note1
Order1	600	2000	Product1 - note2
Order1	600	2000	Product1 - note3
Order1	5000	5000	Product2

但我想要

ORDER	AMOUNT_TO_PRODUCE	PRODUCED_AMOUNT	PRODUCT
Order1	600	2000	Product1 - note1
Order1	600	0	Product1 - note2
Order1	600	0	Product1 - note3
Order1	5000	5000	Product2

Answer 1

您似乎想要找到总生产量并将其加入订单 table 中每个订单和产品 ID 的第一行。如果是这样，您应该：

在加入之前对生产行求和
识别订单中的第一行 table 每个订单和产品 ID，您可以使用 row_number() 分析函数
将两者连接在一起，这将涉及将汇总的生产行与订单进行外部连接 table

你可以这样做：

WITH production AS (SELECT 'Order1' order_num, 1000 produced_amount, 'ProductID1' product_id FROM dual UNION ALL
                    SELECT 'Order1' order_num, 1000 produced_amount, 'ProductID1' product_id FROM dual UNION ALL
                    SELECT 'Order1' order_num, 5000 produced_amount, 'ProductID2' product_id FROM dual),
         orders AS (SELECT 'Order1' order_num, 600 amount_to_produce, 'Product1 - note1' product, 'ProductID1' product_id FROM dual UNION ALL
                    SELECT 'Order1' order_num, 600 amount_to_produce, 'Product1 - note2' product, 'ProductID1' product_id FROM dual UNION ALL
                    SELECT 'Order1' order_num, 600 amount_to_produce, 'Product1 - note3' product, 'ProductID1' product_id FROM dual UNION ALL
                    SELECT 'Order1' order_num, 5000 amount_to_produce, 'Product2' product, 'ProductID2' product_id FROM dual),
    -- end of mimicking your tables; main query below
    prdctn_amts AS (SELECT order_num,
                           SUM(produced_amount) total_produced_amount,
                           product_id
                    FROM   production
                    GROUP BY order_num,
                             product_id),
     order_dets AS (SELECT order_num,
                           amount_to_produce,
                           product,
                           product_id,
                           row_number () OVER (PARTITION BY order_num, product_id ORDER BY product) rn
                    FROM   orders)
SELECT o.order_num,
       o.amount_to_produce,
       NVL(p.total_produced_amount, 0)
       total_produced_amount,
       o.product
FROM   order_dets o
       LEFT OUTER JOIN prdctn_amts p ON o.order_num = p.order_num
                                        AND o.product_id = p.product_id
                                        AND o.rn = 1
ORDER BY o.order_num,
         o.product_id,
         o.rn;

产生以下输出：

ORDER_NUM AMOUNT_TO_PRODUCE TOTAL_PRODUCED_AMOUNT PRODUCT
--------- ----------------- --------------------- ----------------
Order1                  600                  2000 Product1 - note1
Order1                  600                     0 Product1 - note2
Order1                  600                     0 Product1 - note3
Order1                 5000                  5000 Product2

N.B。您不需要 with 子句中的前两个子查询；我添加了它们，这样我就可以模仿您的两个 table，而您只需直接引用这两个 table。此外，由于 ORDER 是 Oracle 中的保留字，我通过将列名更改为 ORDER_NUM 来避免每次需要引用它时都必须使用 " 来封装列名。

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