Sql 将两个select语句连接到一个表中

我想连接两个表以显示一个结果集。任何帮助都将不胜感激

待定订单：

┌─────────┬────────────────┬────────────────┐ │ OrderID │ PublicationID1 │ PublicationID2 │ ├─────────┼────────────────┼────────────────┤ │ 1 │ 1 │ 2 │ │ 2 │ 3 │ 1 │ │ 3 │ 1 │ 3 │ └─────────┴────────────────┴────────────────┘

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您不需要子查询。只需将

tbl_出版物
左连接两次，一次在
PublicationID1
上，另一次在
PublicationID2
上：

SELECT o.OrderID,
       p1.Publication_Name AS PublicationName1,
       p2.Publication_Name AS PublicationName2
FROM tbl_Orders o
LEFT JOIN tbl_Publications p1 ON o.PublicationID1 = p1.PubID
Left JOIN tbl_Publications p2 ON o.PublicationID2 = p2.PubID

您可以像这样使用
连接

SELECT 
    orderId, 
    b.Publication_Name as PublicationName1 
    c.Publication_Name as PublicationName2 
from tbl_Orders a
LEFT JOIN tbl_Publications b ON a.PublicationID1 = b.PubID
Left JOIN tbl_Publications c ON a.PublicationID2 = c.PubID

在大多数情况下，您不会使用
子查询
，因为它们确实会给系统带来沉重负担-因此，如果您可以避免子查询，请在不使用子查询的情况下工作

我会把它移到它下面的一张桌子上，在那里你可以有多个订单项目

订单库存将是指向您自己库存的链接，您还将包括有关价格等的信息，以便进一步的价格变化不会影响您：）
如果您想要子查询，这也会起作用

SELECT ord.Orderid,
(select Publication_Name 
 from tbl_Publications 
 where pubid=ord.PublicationID1) as publication_name1,
 (select Publication_Name 
 from tbl_Publications 
 where pubid=ord.PublicationID2) as publication_name2
FROM tbl_Orders ord

这就解决了…我需要两个左连接！谢谢。
SELECT o.OrderID,
       p1.Publication_Name AS PublicationName1,
       p2.Publication_Name AS PublicationName2
FROM tbl_Orders o
LEFT JOIN tbl_Publications p1 ON o.PublicationID1 = p1.PubID
Left JOIN tbl_Publications p2 ON o.PublicationID2 = p2.PubID

SELECT 
    orderId, 
    b.Publication_Name as PublicationName1 
    c.Publication_Name as PublicationName2 
from tbl_Orders a
LEFT JOIN tbl_Publications b ON a.PublicationID1 = b.PubID
Left JOIN tbl_Publications c ON a.PublicationID2 = c.PubID

SELECT ord.Orderid,
(select Publication_Name 
 from tbl_Publications 
 where pubid=ord.PublicationID1) as publication_name1,
 (select Publication_Name 
 from tbl_Publications 
 where pubid=ord.PublicationID2) as publication_name2
FROM tbl_Orders ord