微信公众号搜"智元新知"关注
微信扫一扫可直接关注哦！

VB查询数据库之组合查询——机房收费总结二

分类：VB作者：编程之家AI导航网

在机房收费系统中，组合查询用的还是挺多的，像上机状态查询窗体、学生上机统计信息窗体、操作员工记录窗体、基本信息维护窗体。这其中，学生基本信息维护窗体中的东西比较多，就以它为例子，说说组合查询吧！

学生基本信息维护窗体如图所示：

先把代码放在下面，然后再解说：

Option Explicit
Private Sub cboField1_Click()       '把选择的字段转换成  sql语句中的字段
    If cboField1.Text = "卡号" Then cboField1.Tag = "cardNo"
    If cboField1.Text = "学号" Then cboField1.Tag = "studentNo"
    If cboField1.Text = "姓名" Then cboField1.Tag = "studentName"
    If cboField1.Text = "性别" Then cboField1.Tag = "sex"
    If cboField1.Text = "学院" Then cboField1.Tag = "college"
    If cboField1.Text = "专业" Then cboField1.Tag = "major"
    If cboField1.Text = "年级" Then cboField1.Tag = "grade"
    If cboField1.Text = "班级" Then cboField1.Tag = "class"
End Sub

Private Sub cboField2_Click()        '把选择的字段转换成  sql语句中的字段
    If cboField2.Text = "卡号" Then cboField2.Tag = "cardNo"
    If cboField2.Text = "学号" Then cboField2.Tag = "studentNo"
    If cboField2.Text = "姓名" Then cboField2.Tag = "studentName"
    If cboField2.Text = "性别" Then cboField2.Tag = "sex"
    If cboField2.Text = "学院" Then cboField2.Tag = "college"
    If cboField2.Text = "专业" Then cboField2.Tag = "major"
    If cboField2.Text = "年级" Then cboField2.Tag = "grade"
    If cboField2.Text = "班级" Then cboField2.Tag = "class"
End Sub
        
Private Sub cboField3_Click()        '把选择的字段转换成  sql语句中的字段
    If cboField3.Text = "卡号" Then cboField3.Tag = "cardNo"
    If cboField3.Text = "学号" Then cboField3.Tag = "studentNo"
    If cboField3.Text = "姓名" Then cboField3.Tag = "studentName"
    If cboField3.Text = "性别" Then cboField3.Tag = "sex"
    If cboField3.Text = "学院" Then cboField3.Tag = "college"
    If cboField3.Text = "专业" Then cboField3.Tag = "major"
    If cboField3.Text = "年级" Then cboField3.Tag = "grade"
    If cboField3.Text = "班级" Then cboField3.Tag = "class"
End Sub

Private Sub cboMode1_Click()            '把选择的字段的组合关系转换成sql中的组合关系关键字，后面可以直接写入查询语句
    If cboMode1.Text = "与" Then cboMode1.Tag = "and"
    If cboMode1.Text = "或" Then cboMode1.Tag = "or"

    cboField2.Visible = True
    cboSign2.Visible = True
    txtInquire2.Visible = True
    cboMode2.Visible = True
End Sub

Private Sub cboMode2_Click()            '把选择的字段组合关系转换成sql中的组合关系关键字，后面可以直接写入查询语句
    If cboMode2.Text = "与" Then cboMode2.Tag = "and"
    If cboMode2.Text = "或" Then cboMode2.Tag = "or"

    cboField3.Visible = True
    cboSign3.Visible = True
    txtInquire3.Visible = True
End Sub

Private Sub cmdClear_Click()     '清空所有的属性
    cboField1.Text = ""
    cboField2.Text = ""
    cboField3.Text = ""
    cboSign1.Text = ""
    cboSign2.Text = ""
    cboSign3.Text = ""
    txtInquire1.Text = ""
    txtInquire2.Text = ""
    cboMode1.Text = ""
    cboMode2.Text = ""
    
    cboField2.Visible = False       '把多查询条件字段先隐藏'隐藏起多字段，这样刚刚开始，只显示第一条查询，如果需要，选择"与"或者"或"，显示下一条字段，同理显示第三条字段。无形中告诉使用者，不要空掉第二条字段，只用一三条，这样会给编码带来麻烦的。
    cboSign2.Visible = False
    txtInquire2.Visible = False
    cboMode2.Visible = False
    
    cboField3.Visible = False
    cboSign3.Visible = False
    txtInquire3.Visible = False
    
    myFlexGrid.Clear
End Sub

Private Sub cmdcharge_Click()
    Dim txtsql As String
    Dim MsgText As String
    Dim mrcSD As ADODB.Recordset
    
    txtsql = "select * from student_Info where studentNo='" & Trim(myFlexGrid.TextMatrix(myFlexGrid.RowSel,0)) & "'"
    Set mrcSD = Executesql(txtsql,MsgText)
    
        If mrcSD.RecordCount = 0 Then
        MsgBox "请选中一条记录!",vbOKCancel + vbExclamation,"警告"
        Exit Sub
    End If
    
    
    frmModifyStudentLog.Show'显示查询窗体
End Sub

Private Sub cmdExit_Click()
    Unload Me
End Sub

Private Sub cmdselect_Click()
    Dim txtsql As String
    Dim MsgText As String
    Dim mrc As ADODB.Recordset
    
    If cboMode1.Text = "" Then
        MsgBox "请输入需要查询的字段",vbOKOnly + vbExclamation,"警告"
       Unload Me
    End If
    
    '首先写一个不完全的sql语句，一会儿补充
    txtsql = "select * from student_Info where (" & cboField1.Tag & cboSign1.Text & "'" & txtInquire1.Text & "'"
    
    If cboMode1.Text <> "" Then      '检验第二个组合字段的正确性
        If cboField2.Text = "" Then
            MsgBox "请选择字段名！","警告"
            cboField2.SetFocus
            Exit Sub
        End If
        If cboSign2.Text = "" Then
            MsgBox "请输入操作符！","警告"
            cboSign2.SetFocus
            Exit Sub
        End If
        If txtInquire2.Text = "" Then
            MsgBox "请输入要查询的内容","警告"
            txtInquire2.SetFocus
            Exit Sub
        End If
        
        '第二个组合字段正确，开始添加信息
        txtsql = txtsql & " " & cboMode1.Tag & " " & cboField2.Tag & cboSign2.Text & "'" & txtInquire2.Text & "'"
    End If
    
    If cboMode2.Text <> "" Then     '检验第三组 组合字段的正确性
        If cboField3.Text = "" Then
            MsgBox "请选择字段名！","警告"
            cboField3.SetFocus
            Exit Sub
        End If
        If cboSign3.Text = "" Then
            MsgBox "请输入操作符！","警告"
            cboSign3.SetFocus
            Exit Sub
        End If
        If txtInquire3.Text = "" Then
            MsgBox "请输入要查询的内容","警告"
            txtInquire3.SetFocus
            Exit Sub
        End If
        
        '第三个组合字段正确，开始添加信息
        txtsql = txtsql & " " & cboMode2.Tag & " " & cboField3.Tag & cboSign3.Text & "'" & txtInquire3.Text & "'"
    End If
    
    txtsql = txtsql & ") "   '把sql语句补充完整
    'Debug.Print txtsql   用于调试程序使用
    Set mrc = Executesql(txtsql,MsgText)
    
    If mrc.RecordCount = 0 Then         '如果要查询的结果为空，则提醒用户
        myFlexGrid.Clear
        MsgBox "结果集为空!","警告"
        Exit Sub
    End If
    
    With myFlexGrid         '把标题写上
        .Row = 0
        .TextMatrix(.Row,0) = "学号"
        .TextMatrix(.Row,1) = "姓名"
        .TextMatrix(.Row,2) = "卡号"
        .TextMatrix(.Row,3) = "余额"
        .TextMatrix(.Row,4) = "学院"
        .TextMatrix(.Row,5) = "年级"
        .TextMatrix(.Row,6) = "班级"
        .TextMatrix(.Row,7) = "性别"
        .TextMatrix(.Row,8) = "状态"
        .TextMatrix(.Row,9) = "备注"
    End With
    
    myFlexGrid.Rows = mrc.RecordCount + 1           '设置大小
    
    With myFlexGrid         '对查询到的结果进行遍历，显示出来
        .Row = 0
        While mrc.EOF = False
            .Row = .Row + 1
            .TextMatrix(.Row,0) = "  " & mrc.Fields(1)
            .TextMatrix(.Row,1) = "  " & mrc.Fields(2)
            .TextMatrix(.Row,2) = "  " & mrc.Fields(0)
            .TextMatrix(.Row,3) = "  " & mrc.Fields(7)
            .TextMatrix(.Row,4) = "  " & mrc.Fields(4)
            .TextMatrix(.Row,5) = "  " & mrc.Fields(5)
            .TextMatrix(.Row,6) = "  " & mrc.Fields(6)
            .TextMatrix(.Row,7) = "  " & mrc.Fields(3)
            .TextMatrix(.Row,8) = "  " & mrc.Fields(11)
            .TextMatrix(.Row,9) = "  " & mrc.Fields(8)
            mrc.MoveNext
        Wend
    End With
End Sub


Private Sub Form_Load()
    cboField1.AddItem "卡号"
    cboField1.AddItem "学号"
    cboField1.AddItem "姓名"
    cboField1.AddItem "性别"
    cboField1.AddItem "学院"
    cboField1.AddItem "专业"
    cboField1.AddItem "年级"
    cboField1.AddItem "班级"
    
    cboField2.AddItem "卡号"
    cboField2.AddItem "学号"
    cboField2.AddItem "姓名"
    cboField2.AddItem "性别"
    cboField2.AddItem "学院"
    cboField2.AddItem "专业"
    cboField2.AddItem "年级"
    cboField2.AddItem "班级"
   
    cboField3.AddItem "卡号"
    cboField3.AddItem "学号"
    cboField3.AddItem "姓名"
    cboField3.AddItem "性别"
    cboField3.AddItem "学院"
    cboField3.AddItem "专业"
    cboField3.AddItem "年级"
    cboField3.AddItem "班级"
    
    
    cboSign1.AddItem "="
    cboSign1.AddItem "<"
    cboSign1.AddItem ">"
    cboSign1.AddItem "<>"
    
    cboSign2.AddItem "="
    cboSign2.AddItem "<"
    cboSign2.AddItem ">"
    cboSign2.AddItem "<>"
    
    cboSign3.AddItem "="
    cboSign3.AddItem "<"
    cboSign3.AddItem ">"
    cboSign3.AddItem "<>"
    
    cboMode1.AddItem "与"
    cboMode1.AddItem "或"
    
    cboMode2.AddItem "与"
    cboMode2.AddItem "或"
End Sub

在编写这个窗体的时候，刚开始总是无法查询，各种报错，后来，看了同学的博客，利用tag将文字语言转换为sql语言，直接写入查询语句，这就方便了很多。之后，在查询的时候，刚开始想直接在窗体中显示所有查询语句，但是，在执行的时候，往往因为第二条空着，而第三条能写入了查询条件而出错。各种限制方法非常麻烦，我就直接限制了窗体显示的语句条数，算是个“懒办法”吧！

这个窗体还真是用了不少时间，刚刚开始是因为不知道如何写查询语句，使用了tag之后，又出现了查询时遍历错误，总之，麻烦还是挺多的。不过，解决了一个窗体，其他的组合查询都差不多了。

我的总结，希望大家帮忙找出缺点，改正后一起进步。下一篇VB写入数据库。

版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 dio@foxmail.com 举报，一经查实，本站将立刻删除。

相关推荐

VB Format函数
Format[$] ( expr [ , fmt ] ) format 返回变体型 format$ 强制返回为文本 -------------------------------- 数字类型的格式化 --------------------------------     固定格式参数：     General Number 普通数字，如可以用来去掉千位分隔号     format$("100,1
vb6/ASP FORMAT MM/DD/YYYY
VB6或者ASP 格式化时间为 MM/dd/yyyy 格式，竟然没有好的办法， Format 或者FormatDateTime 竟然结果和系统设置的区域语言的日期和时间格式相关。意思是尽管你用诸如 Format(Now, "MM/dd/yyyy")，如果系统的设置格式区域语言的日期和时间格式分隔符是"-",那他还会显示为 MM-dd-yyyy     只有拼凑： <%response.write
VB.net 捕获项目全局异常
在项目中添加如下代码：新建窗口来显示异常信息。 Namespace My ‘全局错误处理，新的解决方案直接添加本ApplicationEvents.vb 到工程即可 ‘添加后还需要一个From用来显示错误。如果到这步还不会则需要先打好基础啦 ‘======================================================== ‘以下事件
实现用VB.Net/(C#)开发K/3 BOS 插件的真正可行方法
转了这一篇文章，原来一直想用C#做k3的插件开发，vb没有C#用的爽呀，这篇文章写与2011年，看来我以前没有认真去找这个方法呀。 https://blog.csdn.net/chzjxgd/article/details/6176325 金蝶K3 BOS的插件官方是用VB6编写的，如果  能用.Net下的语言工具开发BOS插件是一件很愉快的事情，其中缘由不言而喻，而本文则是个人首创，实现在了用V
vb，wps，excel 分裂
Sub 分列() ‘以空格为分隔符，连续空格只算1个。对所选中的单元格进行处理 Dim m As Range, tmpStr As String, s As String Dim x As Integer, y As Integer, subStr As String If MsgBox("确定要分列处理吗？请确定分列的数据会覆盖它后面的单元格！", _
VB文件 hash 查看器
  窗体代码 1 Private Sub Text1_OLEDragDrop(Data As DataObject, Effect As Long, Button As Integer, Shift As Integer, X As Single, Y As Single) 2 Dim path As String, hash As String 3 For Each fil
VB.NET MYSQL DataGridView 增删改查INSERT,SELECT,UPDATE,DELETE
  Imports MySql.Data.MySqlClient Public Class Form1 ‘ GLOBAL DECLARATIONS Dim conString As String = "Server=localhost;Database=net2;Uid=root;Pwd=123456;" Dim con As New MySqlConnection
VB.NET 使用ADODB連接資料庫滙出到EXCEL
‘導入命名空間 Imports ADODB Imports Microsoft.Office.Interop   Private Sub A1() Dim Sql As String Dim Cnn As New ADODB.Connection Dim Rs As New ADODB.Recordset Dim S As String   S = "Provider=OraOLEDB.Oracl
vb.net 多线程運用 ping
Imports System.IO Imports System.Threading Imports System.Diagnostics Public Class Form1 Dim A(254) As String    Function ping(ByVal IP As Integer) As String Dim IPAddress As String IPAddress = "10.0.
VB等待进程结束
VB运行EXE程序，并等待其运行结束 参考：https://blog.csdn.net/useway/article/details/5494084 Private Declare Function WaitForSingleObject Lib "kernel32" (ByVal hHandle As Long, ByVal dwMilliseconds As Long) As Long Pr
苹果市值2025年有望达4万亿美元
pythonJavaScriptjavaHTMLreactjsC#AndroidCSSNode.jssqlrpython-3.xMysqLjQueryc++pandasFlutterangularIOSdjangolinuxswifttypescript路由器JSON路由器设置无线路由器h3c华三华三路由器设置华三路由器电脑软件教程arraysdocker软件图文教程Cvue.jslaravelspring-bootreact-native