机房收费系统 之 上下机

         我的上下机可以说是机房收费系统的最后的一部分。在敲上下机之前自己没有去理一理思路，用户是怎样上机的又是怎样下机的，只是听他们说比较难，所以有一点点畏惧的心理，所以一直拖延到了最后。其实，当自己静下心来思考的时候，也没有那么难，最最主要的要有自己的思考。

下面是我对于上下机的流程图分析

下面是上机按钮下的代码实现过程

Dim txtSQL As String     '定义变量    Dim MsgText As String    Dim mrconline As ADODB.Recordset    Dim mrcline As ADODB.Recordset    Dim mrcstudent As ADODB.Recordset    Dim mrccancelcard As ADODB.Recordset         '假如卡号未注册    txtSQL = "select * from student_info where cardno='" & Trim(txtcardno.Text) & "' "    Set mrcstudent = ExecuteSQL(txtSQL, MsgText)    If mrcstudent.EOF Then        MsgBox "此卡未注册！", vbOKOnly + vbExclamation, "警告"        Exit Sub    End If        '假如卡号已经上机    txtSQL = "select * from online_info where cardno='" & Trim(txtcardno.Text) & "' "    Set mrconline = ExecuteSQL(txtSQL, MsgText)    If mrconline.EOF = False Then        MsgBox "此卡已经上机，请重新输入卡号！", vbOKOnly + vbExclamation, "警告"        Exit Sub    End If        '假如已经退卡，不能再上机    txtSQL = "select * from cancelcard_info where cardno='" & Trim(txtcardno.Text) & "' "    Set mrccancelcard = ExecuteSQL(txtSQL, MsgText)    If mrccancelcard.EOF = False Then        MsgBox "此卡已经退卡，请重新输入！", vbOKOnly + vbExclamation, "警告"        Exit Sub    End If        '判断输入情况    If Trim(txtcardno.Text) = "" Then        MsgBox "请输入卡号！", vbOKOnly + vbExclamation, "警告"        txtcardno.SetFocus        Exit Sub          Else        If Len(txtcardno.Text) > 10 Then            MsgBox "卡号不能超过10位数，请重新输入！", vbOKOnly + vbExclamation, "警告"            txtcardno.SetFocus            Exit Sub        End If        txtSQL = "select * from student_info where cardno='" & txtcardno.Text & "'"        Set mrconline = ExecuteSQL(txtSQL, MsgText)                If mrconline.EOF And mrconline.BOF Then  '没有找到相应的卡号            MsgBox "卡号未注册，请重新输入！", vbOKOnly + vbExclamation, "警告"            txtcardno.Text = ""            txtcardno.SetFocus            Exit Sub        End If    End If