如何连接来自多个表的数据，保留所有不同的值

Question

我有三张桌子：

文章：

idArticle
libArticle

库存：

idArticle
idWarehouse
qtyStock

仓库：

idWarehouse
libWarehouse

在表格库存中，我只有文章可用 因此，例如，如果数据是：

文章：

890001 'Article1'
890002 'Article2'

仓库：

0001 'Warehouse Est'
0002 'Warehouse West'
0003 'Warehouse South'

库存：

890001 0001 50
890001 0002 30
890002 0003 20

我想提出一个显示每篇文章的 qtyStock 的请求，如果没有库存，qtyStock 中会显示“0”，并且每个仓库都有一行，例如：

890001 0001 50
890001 0002 30
890001 0003 0
890002 0001 0
890002 0002 0
890002 0003 20

我试过了：

select a.idwarehouse, a.idarticle, s.qtystock  from 
(
select idwarehouse, idarticle
from article, warehouse
where idarticle IN ('890001', '890002')
) a 
left join stock s on a.idwarehouse = s.idwarehouse and a.idarticle = s.idarticle

它可以工作，但是没有这种子请求有没有更好的方法？

Answer 1

结果可以通过文章和仓库的简单CROSS JOIN得到所有组合，然后LEFT JOIN库存。

WITH
    article (idarticle, libarticle)
    AS
        (SELECT '890001', 'Article1' FROM DUAL
         UNION ALL
         SELECT '890002', 'Article2' FROM DUAL),
    stock (idarticle, idwarehouse, qtystock)
    AS
        (SELECT '890001', '0001', 50 FROM DUAL
         UNION ALL
         SELECT '890001', '0002', 30 FROM DUAL
         UNION ALL
         SELECT '890002', '0003', 20 FROM DUAL),
    warehouse (idwarehouse, libwarehouse)
    AS
        (SELECT '0001', 'Warehouse Est' FROM DUAL
         UNION ALL
         SELECT '0002', 'Warehouse West' FROM DUAL
         UNION ALL
         SELECT '0003', 'Warehouse South' FROM DUAL)
  SELECT a.idarticle, w.idwarehouse, NVL (s.qtystock, 0) AS stock
    FROM article a
         CROSS JOIN warehouse w
         LEFT JOIN stock s ON (a.idarticle = s.idarticle AND w.idwarehouse = s.idwarehouse)
ORDER BY a.idarticle, w.idwarehouse;



   IDARTICLE    IDWAREHOUSE    STOCK
____________ ______________ ________
890001       0001                 50
890001       0002                 30
890001       0003                  0
890002       0001                  0
890002       0002                  0
890002       0003                 20