📄 mdprofilterx.htm

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<h3><a name="mdprofilterx"></a>Filter 和 RecordCount 属性范例</h3>
<p>
该范例使用 <b>Filter</b> 属性打开一个新的 <b>Recordset</b>，它基于适用于已有 <b>Recordset</b> 的指定条件。它使用 <b>RecordCount</b> 属性显示两个 <b>Recordsets</b> 中的记录数。该过程运行时需要 FilterField 函数。</p>
<pre>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   ' 使用出版商表中的数据打开记录集。
   strCnn = "Provider=sqloledb;" &amp; _
      "Data Source=srv;Initial Catalog=pubs;User Id=sa;Password=; "
   Set rstPublishers = New ADODB.Recordset
   rstPublishers.CursorType = adOpenStatic
   rstPublishers.Open "publishers", strCnn, , , adCmdTable   ' 充填记录集。
   intPublisherCount = rstPublishers.<span class=cfe><b>RecordCount</b></span>   ' 获得用户输入。
   strCountry = Trim(InputBox( _
      "Enter a country/region to filter on:"))   If strCountry &lt;&gt; "" Then
      ' 打开已筛选的记录集对象。
      Set rstPublishersCountry = _
         FilterField(rstPublishers, "Country", strCountry)      If rstPublishersCountry.<span class=cfe><b>RecordCount</b></span> = 0 Then
         MsgBox "No publishers from that country/region."
      Else
         ' 打印原始记录集和已筛选记录集对象的记录数。
         strMessage = "Orders in original recordset: " &amp; _
            vbCr &amp; intPublisherCount &amp; vbCr &amp; _
            "Orders in filtered recordset (Country = '" &amp; _
            strCountry &amp; "'): " &amp; vbCr &amp; _
            rstPublishersCountry.<span class=cfe><b>RecordCount</b></span>
         MsgBox strMessage
      End If
      rstPublishersCountry.Close   End IfEnd SubPublic Function FilterField(rstTemp As ADODB.Recordset, _
   strField As String, strFilter As String) As ADODB.Recordset   ' 在指定的记录集对象上设置筛选操作并打开一个新的记录集对象。
   rstTemp.<span class=cfe><b>Filter</b></span> = strField &amp; " = '" &amp; strFilter &amp; "'"
   Set FilterField = rstTempEnd Function
</pre>
<p class=indent>
<B><b>注意&nbsp;&nbsp;&nbsp;</b></B>当已知要选择的数据时，使用 SQL 语句打开 <b>Recordset</b> 通常更为有效。该范例说明了如何创建唯一的 <b>Recordset</b> 并从特定的国家（地区）获得记录。</p>
<pre>Public Sub FilterX2()   Dim rstPublishers As ADODB.Recordset
   Dim strCnn As String   ' 使用出版商表中的数据打开记录集。
   strCnn = "Provider=sqloledb;" &amp; _
      "Data Source=srv;Initial Catalog=pubs;User Id=sa;Password=; "
   Set rstPublishers = New ADODB.Recordset
   rstPublishers.CursorType = adOpenStatic
   rstPublishers.Open "SELECT * FROM publishers " &amp; _
      "WHERE Country = 'USA'", strCnn, , , adCmdText
      
   ' 打印记录集中的当前数据。
   rstPublishers.MoveFirst
   Do While Not rstPublishers.EOF
      Debug.Print rstPublishers!pub_name &amp; ", " &amp; _
         rstPublishers!country
      rstPublishers.MoveNext
   Loop   rstPublishers.CloseEnd Sub</pre>
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