修复 SQL 中的重复客户

Question

我在 sql server 上使用 java，我有重复客户的数据库问题 （很多客户是通过以下方式复制的）。 我的桌子是：

CUSTOMER(person_id,customer_id)
ORDER (order_id,person_id )

一个重复的客户看起来像这样：

CUSTOMER(333,040535743)
CUSTOMER(334,040535743)
CUSTOMER(335,040535743)

ORDER (1,333 )
ORDER (2,333 )

ORDER (4,334 )
ORDER (5,334 )
ORDER (6,334 )

ORDER (7,335 )
ORDER (8,335 )
ORDER (9,335 )


CUSTOMER(336,009530650)
CUSTOMER(337,009530650)

ORDER (10,336 )
ORDER (11,336 )
ORDER (12,336 )

ORDER (13,337 )
ORDER (14,337 )
ORDER (15,337 )

333,334,335是同一客户的三行，因为他们有相同的customer_id，我想只保留最后一个客户（335），并使334和333的所有订单都参考333。

我的最终数据应该是：

CUSTOMER(335,040535743)
ORDER (1,335)
ORDER (2,335)

ORDER (4,335)
ORDER (5,335)
ORDER (6,335)

ORDER (7,335 )
ORDER (8,335 )
ORDER (9,335 )



CUSTOMER(337,009530650)

ORDER (10,337)
ORDER (11,337)
ORDER (12,337)

ORDER (13,337 )
ORDER (14,337 )
ORDER (15,337 )

如何为所有重复的客户执行查询？ （我有一个查询返回有重复的 customer_id 的列表）

Answer 1

更新Order 表：

UPDATE o
SET o.person_id = cc.max_person_id
FROM
    [Order] AS o
  JOIN
    Customer AS c
        ON c.person_id = o.person_id
  JOIN
    ( SELECT customer_id
           , MAX(person_id) AS max_person_id
      FROM Customer
      GROUP BY customer_id
    ) AS cc
        ON cc.customer_id = c.customer_id ;

然后，更新Customer 表：

UPDATE c
SET c.person_id = cc.max_person_id
FROM
    Customer AS c
  JOIN
    ( SELECT customer_id
           , MAX(person_id) AS max_person_id
      FROM Customer
      GROUP BY customer_id
    ) AS cc
        ON cc.customer_id = c.customer_id ;

---

之后，最好将Customer(person_id) 定义为PRIMARY KEY 或使用UNIQUE 约束。

还有一个从Order(person_id) 到Customer(person_id) 的FOREIGN KEY 约束

Answer 2

从这里开始：

select person_id from customer where customer_id = 040535743

然后是这样的：

select * from orders where person id in ( select person_id from customer where customer_id = 040535743 )

那么你可以在结果中使用 MAX person_id。