避免在此UNION查詢中進行其他子選擇？

Question

shipping_customer表：

+----+---------------+---------------------+
| id | business_name | billing_customer_id |
+----+---------------+---------------------+
|  1 | Soylent Corp  |                   3 |
|  2 | Initech       |                   4 |
+----+---------------+---------------------+

billing_customer表：

+----+--------------------+
| id |   business_name    |
+----+--------------------+
|  3 | Acme Corporation   |
|  4 | Globex Corporation |
+----+--------------------+

在兩個表中，ID是唯一的。 期望的輸出是id IN (1, 4)每個客戶（如果要運輸，還選擇開票客戶id IN (1, 4) ：

+-------------+--------------------+----------+
|      id     |   business_name    |   type   |
+-------------+--------------------+----------+
|           1 | Soylent Corp       | shipping |
|           3 | Acme Corporation   | billing  | <- 1 has billing_customer = 3
|           4 | Globex Corporation | billing  |
+-------------+--------------------+----------+

有辦法避免子選擇嗎？

SELECT id, business_name, 'shipping' AS type
FROM shipping_customer
WHERE id IN (1, 4)

UNION

SELECT id, business_name, 'billing' AS type
FROM billing_customer
WHERE 
    id IN (1, 4) OR
    id IN (SELECT billing_customer_id from shipping_customer WHERE id IN (1, 4))

Answer 1

他沒有子查詢就問。

碼：

SELECT id, business_name, 'shipping' AS type
FROM shipping_customer
WHERE id IN (1, 4)

UNION ALL

SELECT b.id AS [id], 
       b.business_name AS [business_name],
       'billing' AS [type]
FROM   shipping_customer s 
       JOIN billing_customer b 
              ON s.billing_customer_id = b.id 
WHERE  s.id IN ( 1, 4)
OR     b.id IN ( 1, 4)

您能看到這是否正確嗎？ 對於“想要的輸出就是每個客戶”的含義，我不清楚。 這也可能不是最優化的方法。

Answer 2

您可以UNION三套：

1. 運輸客戶
2. 計費客戶

3. 運送客戶加入到計費客戶

   SELECT id，business_name，'shipping'AS類型，從shipping_customer WHERE id IN（1，4），UNION SELECT id，business_name，'billing'，AS類型，FROM billing_customer WHERE id IN（1，4） ，類型為FROM shipping_customer sc INNER JOIN billing_customer bc on sc.billing_customer_id = bc.id，其中“通過運輸計費”在哪里sc.billing_customer_id IN（1，4）

問題中的查詢是一種很好的顯式方式，我唯一用EXISTS代替IN的方法是：

SELECT id, business_name, 'shipping' AS type
FROM shipping_customer
WHERE id IN (1, 4)
UNION
SELECT id, business_name, 'billing' AS type
FROM billing_customer bc
WHERE 
    id IN (1, 4) OR
    EXISTS (SELECT 1 FROM shipping_customer 
            WHERE bc.id = billing_customer_id AND id IN (1, 4))

Answer 3

如果您使用的是SQL Server 2012+，則可以嘗試以下查詢：

SELECT IIF(customerType = 'sName', scId, bcId) AS id,
       customer,
       IIF (customerType = 'sName', 'shipping', 'billing') AS type
FROM (
   SELECT sc.id AS scId, bc.id AS bcId, 
          sc.business_name AS sName, bc.business_name AS bName
   FROM shipping_customer AS sc
   INNER JOIN billing_customer AS bc ON sc.billing_customer_id = bc.id
) src
UNPIVOT (
   customer FOR customerType IN  (sName, bName)
) unpvt      
WHERE (customerType = 'sName' AND (scId IN (1,4))) 
      OR ((customerType = 'bName') AND ((scId IN (1,4)) OR (bcId IN (1,4))))

在這里演示