Question

我有3张桌子 - 桌子1＆amp;表2中有记录，表3中应该插入差异。这就是我现在所拥有的：

SQL = "INSERT INTO Table3 (Field1,Field2)" & _
      "SELECT Table2.Field1, Table2.Field2" & _
      " FROM Table2 LEFT JOIN Table1 ON Table2.Field1 = Table1.Field1" & _
      " OR Table2.Field2 = Table1.Field2" &_ 
      " WHERE (((Table1.Field1) Is Null) OR ((Table1.Field2) Is Null))" & _
      " AND NOT (Table2.Field1 IS NULL AND Table2.Field2 IS NULL)"

此查询在Table3中成功插入了不匹配的记录，但是当我再次运行此查询并且不应再插入任何内容时，查询仍会在表3中插入1条记录，其中Table1或Table2中的一个字段为Null

如何消除这种情况，哪些是缺陷？

编辑：以下是表格中的样本....

Table1:
CompanyNo    CompanyName
111          Microsoft 
             Apple
333          Oracle

Table2:
CompanyNo    CompanyName
111          Microsoft
222          Apple
333          Oracle
             Intel
555          Google

Then Table3 should result differences:
CompanyNo    CompanyName
222          Apple
             Intel
555          Google

首次运行代码结果是正确的，但是当我再次运行它时，＆＃34;英特尔＆＃34;记录再次显示 - 但它不应该是因为表2中的所有新数据都已经在表1中（我在此查询后对表1执行INSERT和UPDATE，因此＆＃34;英特尔＆＃34;记录已经完成在Table1然后）。

Answer 1

您只需要Table2中的字段，因此我会使用not exists：

select t2.Field1, t2.Field2
from table2 as t2
where not exists (select 1
                  from table1 as t1
                  where (t1.field1 = t2.field1 or t1.field1 is null and t2.field1 is null) or
                        (t1.field2 = t2.field2 or t1.field2 is null and t2.field2 is null)
                 );

如果将NULL比较逻辑移动到on子句，则可能会得到类似的结果。但这在MS Access中可能无法实现。

Answer 2

考虑将追加查询拆分为两个操作，分别捕获表1和表2的差异。现在，您正在尝试将两个差异结合起来，而空插入是位于表1中未引用的选择列上的差异：

table1diffSQL = "INSERT INTO Table3 (Field1,Field2)" & _
                "SELECT Table1.Field1, Table1.Field2" & _
                " FROM Table1 LEFT JOIN Table2 ON Table1.Field1 = Table2.Field1" & _
                " AND Table1.Field2 = Table2.Field2" & _  
                " WHERE ((Table2.Field1) Is Null OR (Table2.Field2) Is Null)"


table2diffSQL = "INSERT INTO Table3 (Field1,Field2)" & _
                "SELECT Table2.Field1, Table2.Field2" & _
                " FROM Table2 LEFT JOIN Table1 ON Table1.Field1 = Table2.Field1" & _
                " AND Table1.Field2 = Table2.Field2" & _
                " WHERE ((Table1.Field1) Is Null OR (Table1.Field2) Is Null)"

编辑（根据OP的样本数据）

SELECT Table2.CompanyNo, Table2.CompanyName
FROM Table2 LEFT JOIN Table1
ON  Table1.CompanyNo = Table2.CompanyNo
AND Table1.CompanyName = Table2.CompanyName
WHERE Table1.CompanyNo Is Null OR Table1.CompanyName Is Null

结果

CompanyNo   CompanyName
      222   Apple
            Intel
      555   Google

Answer 3

我准备了一个小例子，以确保我们在同一页面上。

如果这是您正在寻找的，那么您可以使用UNION ALL。

INSERT INTO Table3
SELECT *
FROM (SELECT Table1.Field1 , Table1.Field2 FROM Table1 LEFT JOIN Table2 ON     
Table1.Field1 = Table2.Field1 WHERE Table2.Field1 is Null 
UNION ALL 
SELECT Table2.Field1 , Table2.Field2 FROM Table2 LEFT JOIN Table1 ON     
Table1.Field1 = Table2.Field1 WHERE Table1.Field1 is Null 
)  AS UnMatchedTable;

正如我之前所说，再次运行它会再次添加相同的记录。

访问SQL - INSERT不匹配的记录

3 个答案: