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 |
+----+--------------------+

两个表中的ID是唯一的。想要输出的是每个客户（如果是运费，也选择结算客户）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  |
+-------------+--------------------+----------+

有没有办法避免subselect？

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

他在没有子查询的情况下提出要求。

代码：

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)

你能看出这是否正确吗？我不明白你的意思是什么'通缉输出是每个客户'。这也可能不是最优化的方法。

Answer 2

你可以使用UNION三套：

送货客户
结算客户
运送客户加入结算客户

SELECT id，business_name，＆＃39; shipping＆＃39; AS类型来自shipping_customer 在哪里id IN（1,4）联盟 SELECT id，business_name，＆＃39; billing＆＃39; AS类型来自billing_customer 哪里 id IN（1,4）联盟 SELECT sc.billing_customer_id， bc.business_name，＆＃39;通过运费结算＆＃39;作为类型来自shipping_customer sc INNER JOIN billing_customer bc on sc.billing_customer_id = bc.id. WHERE sc.billing_customer_id IN（1,4）

问题中的查询是一种很好的明确方式，我唯一能用EXISTS替换IN：

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+，则可以尝试以下查询：

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))))

Demo here

在此UNION查询中避免使用其他子选择？

3 个答案: