mysql - 如何在 MySQL 中查找重复值和更新值

Question

使用此查询:

SELECT ARCustomerCode,
       count(ARCustomerCode)
FROM customers
group by ARCustomerCode
having count(ARCustomerCode) > 1;

我能够识别 ARCustomerCode 不唯一的行数。如何通过附加唯一行 ID 来更新每个重复的 ARCustomerCode 字段？

欣赏洞察力!

Answer 1

您可以利用ROW_NUMBER窗口函数为每个重复的“ARCustomerCode”值分配排名，然后仅更新每个代码的排名 > 1(所有重复项)的记录。

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER(PARTITION BY ARCustomerCode ORDER BY <row_id_col>) AS rn
    FROM customers
)
UPDATE     customers
INNER JOIN cte 
        ON customers.<row_id_col> = cte.<row_id_col>
SET customers.ARCustomerCode = CONCAT(customers.ARCustomerCode, customers.<row_id_col>)
WHERE rn > 1