機房收費系統中有幾個窗體用到查詢。

    查詢需要解決2個問題：

    1、卡號已註冊，即存在該怎樣做   

    2、卡號未註冊，即不存在該怎樣做    

   下面以 學生查詢餘額窗體為例

<span style="font-size:18px;">Private Sub Command1_Click()
   Dim txtSQL As String
   Dim MsgText As String
   Dim mrc As ADODB.Recordset
   
   '判斷卡號收是否為空，是否是數字
   If Trim(Text1.Text) = "" Then
          
         MsgBox "卡號不能為空！", vbOKOnly + vbExclamation, "警告"
         Text1.SetFocus
         Exit Sub
      End If
      
    If Not IsNumeric(Text1.Text) Then
          MsgBox "請輸入數字！", vbOKOnly + vbExclamation, "警告"
          Exit Sub
          Text1.SetFocus
    End If
   txtSQL = "select * from student_Info where cardno= '" & Text1.Text & "'"
   Set mrc = ExecuteSQL(txtSQL, MsgText)
   
   '檢查卡號是否存在
   If mrc.EOF Then
        MsgBox "沒有此卡號，請註冊！", vbOKOnly + vbExclamation, "提示"     ' 若不存在，彈出提示框並清空文字框中內容
        Text2.Text = ""
        Text3.Text = ""
        Text4.Text = ""
        Text5.Text = ""
        Text6.Text = ""
        Text7.Text = ""
        Text7.Text = ""
        Text8.Text = ""
        Text9.Text = ""
        Text10.Text = ""
        
    Else
        Text2.Text = mrc.Fields(1)                                          ' 若存在，進行查詢
        Text3.Text = mrc.Fields(2)
        Text4.Text = mrc.Fields(3)
        Text5.Text = mrc.Fields(4)
        Text6.Text = mrc.Fields(5)
        Text7.Text = mrc.Fields(6)
        Text8.Text = mrc.Fields(10)
        Text9.Text = mrc.Fields(8)
        Text10.Text = mrc.Fields(7)
    End If
   
   mrc.Close                                                                 '關閉資料庫

End Sub</span>