Filter 和 RecordCount 属性范例 (VB)

本范例根据应用于现有 Recordset 的指定条件，使用 Filter 属性来打开新的 Recordset。RecordCount 属性用于显示两个 Recordset 中记录的数目。运行此过程需要 FilterField 函数。

Public Sub FilterX()

    Dim rstPublishers As ADODB.Recordset
    Dim rstPublishersCountry As ADODB.Recordset
    Dim strCnn As String
    Dim intPublisherCount As Integer
    Dim strCountry As String
    Dim strMessage As String

    ' Open recordset with data from Publishers table.
    strCnn = "Provider=sqloledb;" & _
        "Data Source=srv;Initial Catalog=Pubs;User Id=sa;Password=; "
    Set rstPublishers = New ADODB.Recordset
    rstPublishers.CursorType = adOpenStatic
    rstPublishers.Open "publishers", strCnn, , , adCmdTable

    ' Populate the Recordset.
    intPublisherCount = rstPublishers.RecordCount

    ' Get user input.
    strCountry = Trim(InputBox( _
        "Enter a country to filter on:"))

    If strCountry <> "" Then
        ' Open a filtered Recordset object.
        Set rstPublishersCountry = _
            FilterField(rstPublishers, "Country", strCountry)

        If rstPublishersCountry.RecordCount = 0 Then
            MsgBox "No publishers from that country."
        Else
            ' Print number of records for the original
            ' Recordset object and the filtered Recordset
            ' object.
            strMessage = "Orders in original recordset: " & _
                vbCr & intPublisherCount & vbCr & _
                "Orders in filtered recordset (Country = '" & _
                strCountry & "'): " & vbCr & _
                rstPublishersCountry.RecordCount
            MsgBox strMessage
        End If
        rstPublishersCountry.Close

    End If

End Sub

Public Function FilterField(rstTemp As ADODB.Recordset, _
    strField As String, strFilter As String) As ADODB.Recordset

    ' Set a filter on the specified Recordset object and then
    ' open a new Recordset object.
    rstTemp.Filter = strField & " = '" & strFilter & "'"
    Set FilterField = rstTemp

End Function

注意   当要选择的数据已知时，使用 SQL 语句打开 Recordset 通常更为有效。本范例显示如何创建唯一的 Recordset 并从特定的国家（地区）获取记录。

Public Sub FilterX2()

    Dim rstPublishers As ADODB.Recordset
    Dim strCnn As String

    ' Open recordset with data from Publishers table.
    strCnn = "Provider=sqloledb;" & _
        "Data Source=srv;Initial Catalog=Pubs;User Id=sa;Password=; "
    Set rstPublishers = New ADODB.Recordset
    rstPublishers.CursorType = adOpenStatic
    rstPublishers.Open "SELECT * FROM publishers " & _
        "WHERE Country = 'USA'", strCnn, , , adCmdText
       
    ' Print current data in recordset.
    rstPublishers.MoveFirst
    Do While Not rstPublishers.EOF
        Debug.Print rstPublishers!pub_name & ", " & _
            rstPublishers!country
        rstPublishers.MoveNext
    Loop

    rstPublishers.Close

End Sub