Question

我想不通过这个。我有这个问题：

SELECT 
    p.person_id,
    p.first_nm,
    p.last_nm, 
    pu.purchase_dt,
    pr.sku, 
    pr.description,
    a.address_type_id,
    a.city_cd, 
    a.state_cd, 
    a.postal_cd
FROM 
    person p 
    INNER JOIN address a ON p.person_id = a.person_id
    INNER JOIN purchase pu ON pu.person_id = p.person_id
    INNER JOIN product pr ON pr.product_id = pu.product_id

足够简单 - 我只需要为我们发货的客户获取信息。但是，由于addressType表

AddressType

address_type_id    address_type_desc
------------------------------------
1            Home
2            Shipping

某些客户在地址表中有多个地址，因此会创建非唯一的重复条目。

1,Smith, John, 12/01/2009, A12345, Purple Widget, 1, Anywhere, CA, 12345
1,Smith, John, 12/01/2009, A12345, Purple Widget, 2, Somewhere, ID, 54321

我想让查询返回一行/人并返回家庭地址（如果有的话），返回送货地址。

这看起来很简单，也许这只是我的感冒，但这让我有点不知所措。

Answer 1

你想要改变你的联接，所以它返回min（addressID）而不是所有这些：

        INNER JOIN address a ON p.person_id = a.person_id
        inner join (select person_id, min(address_type_id) as min_addr 
from address group by person_id) a_min 
on a.person_id = a_min.person_id and a.address_type_id = a_min.min_addr

Answer 2

SELECT 
    p.person_id,
    p.first_nm,
    p.last_nm, 
    pu.purchase_dt,
    pr.sku, 
    pr.description,
    COALESCE(ha.address_type_id, sa.address_type_id) AS address_type_id
    CASE WHEN ha.address_type_id IS NOT NULL THEN ha.city_cd ELSE sa.city_cd END AS city_cd, 
    CASE WHEN ha.address_type_id IS NOT NULL THEN ha.state_cd ELSE sa.state_cd END AS state_cd, 
    CASE WHEN ha.address_type_id IS NOT NULL THEN ha.postal_cd ELSE sa.postal_cd END AS postal_cd
FROM 
    person p 
    LEFT JOIN address ha ON p.person_id = ha.person_id AND ha.address_type_id = 1
    LEFT JOIN address sa ON p.person_id = sa.person_id AND sa.address_type_id = 2
    INNER JOIN purchase pu ON pu.person_id = p.person_id
    INNER JOIN product pr ON pr.product_id = pu.product_id

Answer 3

如果是SQL Server或具有公用表表达式（CTE）的其他版本，则可以执行以下操作。 CTE添加一个按人员分组并按address_type_id排序的行号列。主要查询被更改为从CTE返回每个人的第1行。

WITH cte AS
    (
    SELECT
         a.person_id,
         a.address_type_id,
         a.city_cd, 
         a.state_cd, 
         a.postal_cd,
         ROW_NUMBER() over (PARTITION BY person_id ORDER BY address_type_id) AS sequence
    FROM address a
    INNER JOIN AddressType at ON a.address_type_id = at.address_type_id
    )

    SELECT 
        p.person_id,
        p.first_nm,
        p.last_nm, 
        pu.purchase_dt,
        pr.sku, 
        pr.description,
        a.address_type_id,
        a.city_cd, 
        a.state_cd, 
        a.postal_cd
    FROM 
        person p 
        INNER JOIN cte a ON p.person_id = a.person_id
        INNER JOIN purchase pu ON pu.person_id = p.person_id
        INNER JOIN product pr ON pr.product_id = pu.product_id
    WHERE
        a.sequence = 1

顺便说一下，如果你有没有地址的人物记录，你可能想要在地址表上将INNER JOIN更改为OUTER JOIN（在我的回答中为cte）。如果您的要求表明，这也适用于购买和产品的连接。

SQL查询帮助处理非唯一重复项

3 个答案: