从嵌套查询更新 MS Access 表

Question

我的 SQL 很生锈。我正在尝试以嵌套查询的形式使用同一表中的 COUNT(*) 更新表中的一行中的计数器。 SQL如下：

UPDATE DWInvoiceHeader AS A
SET A.InvCount = (Select Count(B.HIINV) From DWInvoiceHeader AS B 
                  WHERE (B.HIVENT = '0') 
                  Group By B.HIINV 
                  Order By B.HIINV)
WHERE (A.HIVENT = '0');

行看起来像：

HIINV1.......Seq1.....InvCount   - want InvCount to be 3
HIINV1.......Seq2.....InvCount   - want InvCount to be 3
HIINV1.......Seq3.....InvCount   - want InvCount to be 3
HIINV2.......Seq1.....InvCount   - want InvCount to be 2 
HIINV2.......Seq2.....Invcount   - want InvCount to be 2
.
.
.
HIINVn.......Seq1.....InvCount   - want InvCount to be 1

上面的 SQL 给了我消息“操作必须是可更新的查询”。

有什么想法吗？

Answer 1

UPDATE DWInvoiceHeader AS A
SET A.InvCount = 
(
    Select Count(B.HIINV) 
        From DWInvoiceHeader AS B 
        WHERE (B.HIVENT = '0') AND (A.HIINV = B.HIINV)
        Group By B.HIINV 
)
WHERE (A.HIVENT = '0');

Answer 2

您可以通过以下方式使用域函数 Dcount：

UPDATE test
SET InvCount = Dcount("HIVENT","test","[HIVENT]='0'")

如果您想使用通用方法，那么我建议将计数存储在工作表中，然后更新加入工作表的表。

    Select B.HIINV,Count(B.HIINV) as InvCount 
    into WorkingTbl
    From DWInvoiceHeader AS B 
    WHERE (B.HIVENT = '0') AND (A.HIINV = B.HIINV)
    Group By B.HIINV 

   Update   DWInvoiceHeader  A 
   Inner Join WorkingTbl b 
   on a.HIINV=b.HIINV 
   Set A.InvCount=b.InvCount