机房收费系统中的组合查询也是一大亮点。简单的查询只有一个条件限制，机房收费系统中涉及到的最多的查询条件限制是三个，就一起来揭开他的庐山真面目吧！
【示例界面】
【查询流程】
【函数转换】 【“与”、“或”函数转换】
<span style="font-size:18px;"><strong>Public Function relation(a As String) As String'转换或和与Select Case aCase "与"relation = "and"Case "或"relation = "or"End SelectEnd Function</strong></span> 【查询条件转换】<strong>Public Function filename(strfilename As String)'将选择的查询条件转换为数据库中的字段名Select Case strfilenameCase "教师"filename = "userid"Case "注册日期"filename = "logindate"Case "注册时间"filename = "logintime"Case "注销日期"filename = "logoutdate"Case "注销时间"filename = "logouttime"Case "机器名"filename = "computer"End Select</strong>End Function【三行信息分情况可用】<span style="font-size:18px;"><strong><span style="font-size:18px;">Private Sub cmdQuery_Click()Dim txtsql As StringDim msgtext As StringDim mrc As ADODB.RecordsetDim ctrl As Control</span><span style="font-size:24px;"></span><span style="font-size:18px;"> '第一行可用'判断第一行信息是否有空值If Trim(comField1.Text) = "" Or Trim(comOperate1.Text) = "" Or Trim(txtContent1.Text) = "" ThenMsgBox "请填充完整信息", vbOKOnly + vbExclamation, "警告"Exit SubEnd If'将第一行的信息连接到txtsql中txtsql = "select * from worklog_info where "txtsql = txtsql & filename(comField1.Text) & Trim(comOperate1.Text) & "'" & Trim(txtContent1.Text) & "'"'第二行可用If Trim(comRelation(0).Text) <> "" Then'判断第二行信息是否有空值If Trim(comField2.Text) = "" Or Trim(comOperate2.Text) = "" Or Trim(txtContent2.Text) = "" ThenMsgBox "请填充完整信息", vbOKOnly + vbExclamation, "警告"Exit SubEnd Iftxtsql = txtsql & relation(comRelation(0).Text) & " " & filename(comField2.Text) & Trim(comOperate2.Text) & "'" & Trim(txtContent2.Text) & "'"End If'第三行可用If Trim(comRelation(1).Text) <> "" Then'判断第三行信息是否有空值If Trim(comField3.Text) = "" Or Trim(comOperate3.Text) = "" Or Trim(txtContent3.Text) = "" ThenMsgBox "请填充完整信息", vbOKOnly + vbExclamation, "警告"Exit SubEnd Iftxtsql = txtsql & " " & relation(comRelation(1).Text) & " " & filename(comField3.Text) & comOperate3.Text & "'" _& txtContent3.Text & "'"End IfSet mrc = Executesql(txtsql, msgtext)'当没有记录的时候If mrc.EOF ThenMsgBox "没有此记录", vbOKOnly + vbExclamation, "警告"'清除一类控件For Each ctrl In Me.ControlsIf TypeOf ctrl Is TextBox Or TypeOf ctrl Is ComboBox Thenctrl.Text = ""End IfNext'清空myflexgrid控件MyFlexGrid.ClearCall Form_LoadExit SubEnd IfWith MyFlexGrid'设置列宽度For i = 0 To 8MyFlexGrid.ColWidth(i) = 1500Next i'添加第一行信息.Rows = 1.CellAlignment = 4.TextMatrix(0, 0) = "序列号".TextMatrix(0, 1) = "教师".TextMatrix(0, 2) = "级别".TextMatrix(0, 3) = "注册日期".TextMatrix(0, 4) = "注册时间".TextMatrix(0, 5) = "注销日期".TextMatrix(0, 6) = "注销时间".TextMatrix(0, 7) = "机器名".TextMatrix(0, 8) = "状态"'将查询到的信息添加到控件中Do While Not mrc.EOF.Rows = .Rows + 1.CellAlignment = 4On Error Resume Next.TextMatrix(.Rows – 1, 0) = Trim(mrc.Fields("serial")).TextMatrix(.Rows – 1, 1) = Trim(mrc.Fields("userid")).TextMatrix(.Rows – 1, 2) = Trim(mrc.Fields("level")).TextMatrix(.Rows – 1, 3) = Trim(mrc.Fields("logindate")).TextMatrix(.Rows – 1, 4) = Trim(mrc.Fields("logintime")).TextMatrix(.Rows – 1, 5) = Trim(mrc.Fields("logoutdate")).TextMatrix(.Rows – 1, 6) = Trim(mrc.Fields("logouttime")).TextMatrix(.Rows – 1, 7) = Trim(mrc.Fields("computer")).TextMatrix(.Rows – 1, 8) = Trim(mrc.Fields("status"))mrc.MoveNextLoopmrc.CloseEnd With</span><span style="font-size:24px;">End Sub</span></strong></span>【总结】唯有讲述此间途经的美景，分享没有男主角的相片。
