Question

我有以下内容：

stock   |   Customer   
12345   |   NULL
12345   |   ABC

我想要做的是在没有影响第二个的情况下删除第一个，只要有一组这样的行：

 if exists (select stock   from table WHERE stock='12345' AND Customer   is not null )
            BEGIN
                DELETE FROM table WHERE stock= '12345' AND  Customer    is null
            END

查询有效，但如何更改它以便我不必指定库存？我希望将行保留为null客户是它是与该股票相关联的唯一值。

Answer 1

您可以使用exists：

DELETE t0
FROM table t0
WHERE Customer IS NULL
AND EXISTS
(
    SELECT 1
    FROM table t1
    WHERE t0.stock = t1.stock
    AND t1.Customer IS NOT NULL
)

这只会删除客户为空的记录，并且至少有一条记录具有相同的库存ID。

Answer 2

请检查CTE表达式中的以下SQL DELETE命令我使用了SQL Count function with Partition By子句。为了测试NOT NULL客户字段值，我计算了每个库存的文件名，使我能够删除NULL

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Answer 3

使用以下内容：

WITH CTE (stock, customer, DuplicateCount)
AS
(
SELECT stock, customer,
ROW_NUMBER() OVER(PARTITION BY Stock ORDER BY customer desc) AS DuplicateCount
FROM [Table]
)
DELETE
FROM CTE
WHERE DuplicateCount > 1 and customer is NULL
GO

Answer 4

您可以按如下方式使用cross join：

    DELETE
    FROM mytable
    WHERE stock IN (
            SELECT m2.stock
            FROM mytable m1
            CROSS JOIN mytable m2
            WHERE m1.customer IS NULL
            GROUP BY m2.stock
            HAVING count(m2.stock) > 1
            )
    AND customer is NULL

Answer 5

如果这是您唯一的要求，请执行delete from table where customer is null。

根据另一行删除一行

5 个答案: