DLookup 多条件运行时错误

Question

我正在尝试在 Access 2010 中创建具有多个条件的 DLookup，但遇到了一些麻烦。我通过表格创建发票。在发票表单上，我选择 AccountID，并设置计费月份和年份。根据这些信息，我想搜索我的预付款查询 (quePrepayment) 并提取符合这三个条件的任何预付款。

我目前收到此错误：

运行时错误“3075”： 查询表达式“AccountID= & Forms![frmInvoices]!AccountID & Billing_Month = & Forms![frmInvoices]!Billing_Month & Billing_Year = & Forms![frmInvoices]!Billing_Year)”中的语法错误（缺少运算符）

Private Sub AccountID_Change()
Billing_Prepayment = DLookup("Total_Prepayment", "quePrepayment", "[AccountID] = & Forms![frmInvoices]!AccountID And [Billing_Month] = & Forms![frmInvoices]!Billing_Month And [Billing_Year] = & Forms![frmInvoices]!Billing_Year")
End Sub

Answer 1

将第三个DLookup 参数设为一个字符串，其中内置了Forms![frmInvoices] 控件引用。 （数据库引擎在计算表达式时可以取消引用这些控件。）

Billing_Prepayment = DLookup("Total_Prepayment", "quePrepayment", _
    "[AccountID] = Forms![frmInvoices]!AccountID And [Billing_Month] = Forms![frmInvoices]!Billing_Month And [Billing_Year] = Forms![frmInvoices]!Billing_Year")

但是，该字符串太长了，很难确定它是否正确构建。您可以改用这样的方法...

Dim strCriteria As String
strCriteria = "[AccountID] = Forms![frmInvoices]!AccountID " & _
    "And [Billing_Month] = Forms![frmInvoices]!Billing_Month " & _
    "And [Billing_Year] = Forms![frmInvoices]!Billing_Year")
Debug.Print strCriteria
Billing_Prepayment = DLookup("Total_Prepayment", "quePrepayment", _
    strCriteria)

如果遇到问题，您可以转到立即窗口 (Ctrl+g) 来检查为 strCriteria 构建的内容。