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我有一个包含多个列表框的表单。列表框具有来自传递查询的 SELECT 语句的行源，该查询针对 SQL 数据库运行 EXEC 语句。

由于性能问题，我们一直在使用 SQL Server Profiler 监控服务器，并注意到当您在 VBA 代码中的列表框上运行 .Requery 时，它实际上会运行两次 TSQL EXEC 语句。我逐行浏览了 VBA 代码，并证明是一行代码 (listbox.requery) 创建了多个调用。

有没有人遇到过这个和/或有任何解决方案的想法。

为了进一步说明，列表框的行源设置为“SELECT * FROM qsptTestQuery”。我有一个 Access 查询对象（例如名为 qsptTestQuery），它是返回行的传递查询。在 vba 代码中，我将此对象的 .SQL 设置为“Exec spTestProc 1234”，然后运行 ​​listbox.requery。当我运行 listbox.requery 代码行时，它会在分析器中触发 2 个调用。

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一种解决方案是在 VBA 中自己调用传递查询，从而让您控制何时调用它。ListBox 支持可以填充列表的自定义编写函数。有关如何指定和编写函数的详细信息，请转到此处。

这可以让您更好地控制列表的数量，但我记得它不一定会删除重复调用。换句话说，你可能会发现它在初始化代码中多次调用了这个函数。通过跟踪调用，您也许可以确定模式并编写缓存值的代码，并且仅在必要时重新执行传递查询。

以下是一个旧应用程序的示例，其中包含我的一些评论，我希望它们对编写您自己的应用程序有用。我只需要使用过一次（在许多 ListBox 和 ComboBox 控件中），但效果很好。

Private Function ListBoxResult(Ctr As Control, ID As Variant, Row As Variant, Col As Variant, code As Variant) As Variant
  '* listActionItems.[Row Source Type]
  '* Called to populate listActionItems

  '* PARAMETERS:
  '* Ctr:  A control variable that refers to the list box or combo box being filled.
  '* Id:   A unique value that identifies the control being filled. This is useful when you want to use the same user-defined function for more than one list box or combo box and must distinguish between them. (The example sets this variable to the value of the Timer function.)
  '* Row:  The row being filled (zero-based).
  '* Col:  The column being filled (zero-based).
  '* Code: An intrinsic constant that specifies the kind of information being requested.

  '* https://msdn.microsoft.com/en-us/library/office/ff845731.aspx
  '* Microsoft Access calls your user-defined function once for acLBInitialize, acLBOpen, acLBGetRowCount, and acLBGetColumnCount. It initializes the user-defined function, opens the query, and determines the number of rows and columns.
  '* Microsoft Access calls your user-defined function twice for acLBGetColumnWidth — once to determine the total width of the list box or combo box and a second time to set the column width.
  '* The number of times your user-defined function is called for acLBGetValue and acLBGetFormat to get list entries and to format strings varies depending on the number of entries, the user's scrolling, and other factors.
  '* Microsoft Access calls the user-defined function for acLBEnd when the form is closed or each time the list box or combo box is queried.
  '* Whenever a particular value (such as the number of columns) is required, returning Null or any invalid value causes Microsoft Access to stop calling the user-defined function with that code.

  Static days As Integer
  Static dt As Date
  Static result As Variant

  Select Case code
    Case acLBInitialize '0
      '* Return Nonzero if the function can fill the list; False (0) or Null otherwise.

      result = True
    Case acLBOpen '1
      '* Return Nonzero ID value if the function can fill the list; False or Null otherwise.
      result = True

    Case acLBGetRowCount '3
      If rsTemplateActions Is Nothing Then
        result = 0
      Else
        On Error Resume Next
        result = rsTemplateActions.RecordCount
        If Err.number <> 0 Then
          result = 0
        End If
      End If

    Case acLBGetColumnCount '4
      '* Columns: Action Type, Scheduled Date, Description, Priority
      result = 5

    Case acLBGetColumnWidth '5
      '* 1440 is twips per inch; -1 is default
      Select Case Col
        Case 0: result = 1.5 * 1440
        Case 1: result = 0.8 * 1440
        Case 2: result = 1# * 1440
        Case 3: result = 1.8 * 1440
        Case 4: result = 0.6 * 1440
        Case Else
          result = -1
      End Select

    Case acLBGetValue '6
      result = "-"

      If Not rsTemplateActions Is Nothing Then
        On Error Resume Next
        rsTemplateActions.MoveFirst
        If Err.number = 0 Then
          If Row > 0 Then rsTemplateActions.Move Row

          Select Case Col
            Case 0 'Action Type
              result = rsTemplateActions![Type Text]
            Case 1
              days = 0
              If IsNumeric(rsTemplateActions![DaysAdded]) Then
                days = rsTemplateActions![DaysAdded]
                result = "+" & days & " days"
              Else
                result = "?"
              End If
            Case 2 'Scheduled Date
              days = 0
              If IsNumeric(rsTemplateActions![DaysAdded]) Then
                days = rsTemplateActions![DaysAdded]
              End If
              If IsDate(txtActionDate.value) Then
                dt = CDate(txtActionDate.value)
                dt = DateAdd("d", days, dt)
                result = Format(dt, "mm/dd/yyyy")
              Else
                result = "?"
              End If
              Err.Clear
            Case 3 'Descrip
              result = rsTemplateActions!Description
            Case 4 'Priority
              result = ActionPriority(rsTemplateActions!Priority)
          End Select
        End If
      End If

    Case acLBGetFormat '7
      '* 1440 is twips per inch
      Select Case Col
        Case Else
          result = -1 'Default format
      End Select

    Case acLBEnd '9
      '* Only called when form is closed, not for each requery (I suppose for closing resources)
      'On Error Resume Next

    'Case acLBClose '8
    '  'NOT USED according to online resources.
    'Case Else
    '  Debug.Print "ListBoxResult Code = " & Code
  End Select

  ListBoxResult = result

End Function
于 2018-08-11T05:47:16.713 回答