SQL Server：多个 WHERE NOT EXISTS 子句

Question

Load_Charges_IMPORT 查询中有大约 2600 行没有插入到Load_Charges 查询中。

我试图确保没有添加重复的主键条目。主键在Load_Charges 查询中建立为复合键（收费说明 + 收费金额）。 Load_Charges_IMPORT 查询中未设置任何键，并且此数据是从 Excel 文档中导入的。

当我知道Load_Charges_IMPORT 中有 2600 多行时，您能否告诉我我的代码是否有问题以及为什么我会收到0 row(s) affected 的响应。

INSERT INTO Load_Charges
    SELECT *
    FROM Load_Charges_IMPORT
    WHERE 
        NOT EXISTS (SELECT [Load ID]
                    FROM Load_Charges
                    WHERE Load_Charges_IMPORT.[Load ID] = Load_Charges.[Load ID])
        AND NOT EXISTS (SELECT [Charge Description]
                        FROM Load_Charges
                        WHERE Load_Charges_IMPORT.[Charge Description] = Load_Charges.[Charge Description])
        AND NOT EXISTS (SELECT [Charged Amount] 
                        FROM Load_Charges
                        WHERE Load_Charges_IMPORT.[Charged Amount] = Load_Charges.[Charged Amount]);

Answer 1

解决此问题的另一种方法是使用一系列LEFT JOINs，并带有一个排除任何匹配记录的WHERE 子句。

这是一种较短的语法，并且避免使用子查询。

INSERT INTO Load_Charges
SELECT imp.*
FROM 
    Load_Charges_IMPORT imp
    LEFT JOIN Load_Charges load1 ON load1.[Load ID] = imp.[Load ID]
    LEFT JOIN Load_Charges load2 ON load2.[Charge Description] = imp.[Charge Description]
    LEFT JOIN Load_Charges load3 ON load3.[Charged Amount]= imp.[Charged Amount]
WHERE load1.[Load ID] IS NULL AND load2.[Load ID] IS NULL AND load3.[Load ID] IS NULL
;

NB ：这假定 [Load ID] 是 Load_Charges 表中的不可为空的字段。如果不是，则可以在WHERE 子句中使用任何其他不可为空的字段。

Answer 2

您的 EXISTS 子句排除任何一个条件为 TRUE 的所有行，而不仅仅是所有条件都为 TRUE 的行。试试这个：

INSERT INTO Load_Charges

SELECT *

FROM Load_Charges_IMPORT

WHERE NOT EXISTS (
    SELECT * 
    FROM Load_Charges 
    WHERE Load_Charges_IMPORT.[Load ID]=Load_Charges.[Load ID]
    AND Load_Charges_IMPORT.[Charge Description]=Load_Charges.[Charge Description]
    AND Load_Charges_IMPORT.[Charged Amount]=Load_Charges.[Charged Amount]);