SQL 连接查询；订单与发票

Question

我在编写 SQL 联接查询方面有点新手，我需要有关联接查询的帮助。这是表格。

Table : Txn
TXN_KEY     TYPE      DATE
--------------------------
111          OD       10/5   
221          CS       11/5 
112          OD       12/5
222          CS       12/5

Table: TxnAssociation
TXN_KEY      REF_TXN_KEY     TYPE
---------------------------------
221           111             OS

输入OD 是订单，CS 是客户销售。有一些未结订单，也有一些没有订单的销售。

需要一个连接查询来获得类似的输出

ORD      SAL
--------------
111      221
112      null
null     222

我正在使用德比。我尝试了一些东西，但不值得调试。有没有人可以帮忙...

Answer 1

好的，这个没有全连接

  SELECT orders.TXN_KEY as ORD,ta.TXN_KEY as SAL
    FROM Txn orders 
    LEFT JOIN TxnAssociation ta ON orders.TXN_KEY = ta.REF_TXN_KEY 
   WHERE isnull(orders.Type,'OD') = 'OD'
UNION ALL 
  SELECT NULL  as ORD,sales.TXN_KEY as SAL
    FROM Txn sales
   WHERE sales.Type= 'CS'
 AND NOT EXISTS (SELECT 1 
                   FROM Txn s 
                   JOIN TxnAssociation t ON s.TXN_KEY = t.TXN_KEY 
                                            AND s.Type= 'CS' AND sales.TXN_KEY = s.TXN_KEY)

这个更好：

SELECT orders.TXN_KEY as ORD,ta.TXN_KEY as SAL
  FROM Txn orders 
  LEFT JOIN TxnAssociation ta ON orders.TXN_KEY = ta.REF_TXN_KEY 
 WHERE isnull(orders.Type,'OD') = 'OD'
UNION ALL 
SELECT ta.REF_TXN_KEY  as ORD,sales.TXN_KEY as SAL
 FROM Txn sales
 LEFT JOIN TxnAssociation ta ON sales.TXN_KEY = ta.TXN_KEY
WHERE sales.Type= 'CS'
  AND ta.REF_TXN_KEY is null

Answer 2

试试这个

   SELECT orders.TXN_KEY as ORD, sales.TXN_KEY as SAL
     FROM TxnAssociation ta
     FULL JOIN Txn orders ON orders.TXN_KEY = ta.REF_TXN_KEY 
     FULL JOIN Txn sales ON sales.TXN_KEY = ta.TXN_KEY 
    WHERE isnull(orders.Type,'OD') = 'OD'
      AND isnull(sales.Type,'CS') = 'CS'