VB.NET版机房收费系统---组合查询

       查询的意思就是查找，寻找，指在某一个或几个地方找出自己所要的信息，假如我想搜索一下我自己写的博客，名字叫做初雪之恋，我在百度的搜索框中输入丁国华三个字，会有怎样的惊喜等着我？

        

       

          啊哦，这个信息并不是我想要的，于是我再搜，“丁国华 廊坊师范学院  csdn”搜索结果如下：

        

           很显然，这个还不是我想要的结果，我接着搜，“丁国华 廊坊师范学院 csdn 初雪之恋”；

        

        在我的理解中，组合查询就是通过条件层层限制，一步一步精确，得到我们想要的答案，在机房收费系统中，有好几处涉及组合查询，接下来，以学生基本信息维护为例，讲解组合查询。在第二次机房收费系统中，我没有按原来胡阳版的模板来，原版的通过卡号，学号，姓名，性别，系别，年级，班号七个字段，来进行查询，操作符分别为等于，大于，小于，不等于，可是，现实生活中哪有性别大于什么，姓名小于什么的条件，所以我重新设计了一下窗体，从中挑选了四个字段名作为组合查询的条件简化了组合查询的难度，主界面设计如下：

         

         接下来，看看我们的具体实现过程，首先实体层---E层；

           

<span style="font-size:18px;">Public Class Studentinfo    Public studentNo As String                      '字段    Public Property _studentNo As String            '属性        Get            Return studentNo        End Get        Set(value As String)            studentNo = value        End Set    End Property    Public cardNo As String    Public Property _cardNo As String        Get            Return cardNo        End Get        Set(value As String)            cardNo = value        End Set    End Property    Public studentName As String    Public Property _studentName As String        Get            Return studentName        End Get        Set(value As String)            studentName = value        End Set    End Property    Public sex As String    Public Property _sex As String        Get            Return sex        End Get        Set(value As String)            sex = value        End Set    End Property    Public department As String    Public Property _department        Get            Return department        End Get        Set(value)            department = value        End Set    End Property    Public grade As String    Public Property _grade        Get            Return grade        End Get        Set(value)            grade = value        End Set    End Property    Public stuclass As String    Public Property _stuclass        Get            Return stuclass        End Get        Set(value)            stuclass = value        End Set    End Property    Public remark As String    Public Property _remark        Get            Return remark        End Get        Set(value)            remark = value        End Set    End Property    Public Handler As String    Public Property _Handler        Get            Return Handler        End Get        Set(value)            Handler = value        End Set    End PropertyEnd Class</span>

         数据访问层---D层

           

<span style="font-size:18px;">Imports System.Data.SqlClientPublic Class StuBaInforPreserveDAO    Public Function query(ByVal cmbOperator1 As String, ByVal cardNo As String, ByVal cmbOperator2 As String, ByVal studentNo As String, ByVal cmbOperator3 As String, ByVal department As String, ByVal cmbOperator4 As String, ByVal grade As String) As DataTable        Dim db As New Entity.Dbutil '实例化数据库连接        Dim dt As New DataTable       '实例化DataTable        Using conn As New SqlConnection(db.connstring)            conn.Open()                       '打开数据库连接            Dim sql As String            Dim cmd As SqlCommand            Dim dataAdpter As New SqlDataAdapter            Dim dst As New DataSet            Dim flag(3) As Boolean             ’定义标签            sql = "select studentNo,cardNo,studentName,sex,department,grade,class,remark,handler  from Student_info where "            If Not (cardNo = "") Then                                   '如果卡号不为空，执行下面这句sql语句                sql = sql & "studentNo" & cmbOperator1 & "'" & cardNo & "'"                flag(0) = True            End If            If Not (studentNo = "") Then     '如果学号不为空，且卡号不为空，执行第一个sql语句，如果学号不为空，卡号为空执行第二个sql语句                flag(1) = True                If flag(0) = True Then                    sql = sql & "and studentNo " & cmbOperator2 & "'" & studentNo & "'"                Else                    sql = sql & "studentNo" & cmbOperator2 & "'" & studentNo & "'"                End If            End If            If Not (department = "") Then '如果系别不为空，且学号和卡号中有一个被选择，或者两个都选，执行第一个sql语句，否则执行第二个sql语句                flag(2) = True                If flag(0) = True Or flag(1) = True Then                    sql = sql & "and department " & cmbOperator3 & "'" & department & "'"                Else                    sql = sql & "department" & cmbOperator3 & "'" & department & "'"                End If            End If            If Not (grade = "") Then      '如果年级不为空，且学号，卡号，系别中有一个被选择，或者一个or两个被选择执行第一个sql语句，否则执行第二句                flag(3) = True                If flag(0) = True Or flag(1) = True Or flag(2) = True Then                    sql = sql & "and grade" & cmbOperator4 & "'" & grade & "'"                Else                    sql = sql & "grade" & cmbOperator4 & "'" & grade & "'"                End If            End If            cmd = New SqlCommand(sql, conn)            dataAdpter.SelectCommand = cmd            dataAdpter.Fill(dst, "Student_info")            dt = dst.Tables("Student_info")        End Using        Return dt    End FunctionEnd Class</span>

            业务逻辑层---B层；

             

<span style="font-size:18px;">Public Class StuBaInforPreserveManager    Public Function query(ByVal cmbOperator1 As String, ByVal cardNo As String, ByVal cmbOperator2 As String, ByVal studentNo As String, ByVal cmbOperator3 As String, ByVal department As String, ByVal cmbOperator4 As String, ByVal grade As String) As DataTable        Dim StuBaInforPreserveDAO As New DAL.StuBaInforPreserveDAO                 '调用D层        Return StuBaInforPreserveDAO.query(cmbOperator1, cardNo, cmbOperator2, studentNo, cmbOperator3, department, cmbOperator4, grade)    End FunctionEnd Class</span>

        显示层---U层；

       

<span style="font-size:18px;">Imports BLLPublic Class frmStuBaInforPreserve    Private Sub btnInquery_Click(sender As Object, e As EventArgs) Handles btnInquery.Click        Dim StuBaInforPreserveManager As New BLL.StuBaInforPreserveManager  '调用B层        Dim dt As New DataTable        dt = StuBaInforPreserveManager.query(cmbOperator1.Text, txtCardNo.Text, cmbOperator2.Text, txtStuNo.Text, cmbOperator3.Text, txtDepartment.Text, cmbOperator4.Text, txtGrade.Text)        DataGridView1.AutoGenerateColumns = True  '自动创建列        DataGridView1.DataSource = dt        DataGridView1.Columns(0).HeaderText = "学号"         '把相关信息在datagridview中显示出来        DataGridView1.Columns(1).HeaderText = "卡号"        DataGridView1.Columns(2).HeaderText = "姓名"        DataGridView1.Columns(3).HeaderText = "性别"        DataGridView1.Columns(4).HeaderText = "系别"        DataGridView1.Columns(5).HeaderText = "年级"        DataGridView1.Columns(6).HeaderText = "班级"        DataGridView1.Columns(7).HeaderText = "备注"    End Sub    Private Sub frmStuBaInforPreserve_Load(sender As Object, e As EventArgs) Handles MyBase.Load        cmbOperator1.Enabled = False             '窗体加载时，需要注意的一些细节问题，比如那些按钮能点，那些不能点        txtCardNo.Text = ""        txtCardNo.Enabled = False        cmbOperator1.Items.Add("=")        cmbOperator1.Items.Add(">")        cmbOperator1.Items.Add("<")        cmbOperator1.Items.Add("<>")        cmbOperator1.SelectedIndex = 0        cmbOperator2.Enabled = False        txtStuNo.Text = ""        txtStuNo.Enabled = False        cmbOperator2.Items.Add("=")        cmbOperator2.Items.Add(">")        cmbOperator2.Items.Add("<")        cmbOperator2.Items.Add("<>")        cmbOperator2.SelectedIndex = 0        cmbOperator3.Enabled = False        txtDepartment.Text = ""        txtDepartment.Enabled = False        cmbOperator3.Items.Add("=")        cmbOperator3.Items.Add("<>")        cmbOperator3.SelectedIndex = 0        cmbOperator4.Enabled = False        txtGrade.Text = ""        txtGrade.Enabled = False        cmbOperator4.Items.Add("=")        cmbOperator4.Items.Add("<>")        cmbOperator4.SelectedIndex = 0    End Sub    Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click        '退出按钮        Me.Close()    End Sub    Private Sub chkCardNo_Click(sender As Object, e As EventArgs) Handles chkCardNo.Click  '如果卡号被选中，则txtCardNo和cmbOperator1可以点否者不能点，并且文本框的内容自动情况，恢复默认值        If chkCardNo.Checked Then            txtCardNo.Enabled = True            cmbOperator1.Enabled = True        Else            txtCardNo.Enabled = False            cmbOperator1.Enabled = False            txtCardNo.Text = ""            cmbOperator1.SelectedIndex = 0        End If    End Sub    Private Sub chkStuNo_Click(sender As Object, e As EventArgs) Handles chkStuNo.Click        If chkStuNo.Checked Then            txtStuNo.Enabled = True            cmbOperator2.Enabled = True        Else            txtStuNo.Enabled = False            cmbOperator2.Enabled = False            txtStuNo.Text = ""            cmbOperator2.SelectedIndex = 0        End If    End Sub       Private Sub chkDepartment_Click(sender As Object, e As EventArgs) Handles chkDepartment.Click        If chkDepartment.Checked Then            txtDepartment.Enabled = True            cmbOperator3.Enabled = True        Else            txtDepartment.Enabled = False            cmbOperator3.Enabled = False            txtDepartment.Text = ""            cmbOperator3.SelectedIndex = 0        End If    End Sub    Private Sub chkGrade_Click(sender As Object, e As EventArgs) Handles chkGrade.Click        If chkGrade.Checked Then            txtGrade.Enabled = True            cmbOperator4.Enabled = True        Else            txtGrade.Enabled = False            cmbOperator4.Enabled = False            txtGrade.Text = ""            cmbOperator4.SelectedIndex = 0        End If    End SubEnd Class</span>

      运行效果如下：

      

      自此学生基本信息维护就暂时告一段落，开始敲学生基本信息维护的时候，不知道从哪儿下手，各种纠结，各种逃避，各种不想敲，可是，我已经长大了，我不能再由着我自己的性子来做事，我要为我自己做的事情负责任，走过去了，真的有那么困难么？我想其中的滋味只有走过的人才能够真正明白。

       曾经看到米老师给一篇博文这样的评语，这篇博客的主要内容，我记不清楚了，好像是解决一个问题，然后成功解决的一篇博文，米老师说，这个过程是不是很养人，对，这个过程不光养人，而且锻炼人，考验我们面对新知识的心态，是一拖再拖，今目标红了又红，还是坦然面对，两天把三个组合查询一一搞定，机房收费系统未完，待续......