我个人一直认为，组合查询是机房收费系统的一个难点，尤其是用到三层之后，如果要为组合查询中的每一个查询建立一个显然是太麻烦了。

下面介绍一下我的方法，对大家起个参考作用。

我将该表中可输入的内容定义为一个类，这样调用一次B层和D层就可以了完成查询了。

我以学生上机记录查询为例

1、UI层

Public Class FrmQuerryRecALLStuUPProtected Overrides Sub cmdQuerry_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)TrymyGrid.Columns.Clear()myGrid.Columns.Add("卡号", "卡号")myGrid.Columns.Add("学号", "学号")myGrid.Columns.Add("学生姓名", "学生姓名")myGrid.Columns.Add("性别", "性别")myGrid.Columns.Add("上机日期", "上机日期")myGrid.Columns.Add("上机时间", "上机时间")myGrid.Columns.Add("上机日期", "下机日期")myGrid.Columns.Add("下机日期", "下机时间")myGrid.Columns.Add("消费金额", "消费金额")' myGrid.Columns.Add("操作员", "操作员")'''''''''''''''将组合框中内容传递到UQuery参数''''''''''''''''''Dim UQuery As New Entity.Entity_QueryCompositonUQuery.Combine1 = Trim(cobCombine1.Text)UQuery.Combine2 = Trim(cobCombine2.Text)UQuery.FiledName1 = Trim(cobFild1.Text)UQuery.FiledName2 = Trim(cobFild2.Text)UQuery.FiledName3 = Trim(cobFild3.Text)UQuery.Operator1 = Trim(cobOperator1.Text)UQuery.Operator2 = Trim(cobOperator2.Text)UQuery.Operator3 = Trim(cobOperator3.Text)UQuery.QueryContent1 = Trim(TextBox1.Text)UQuery.QueryContent2 = Trim(TextBox2.Text)UQuery.QueryContent3 = Trim(TextBox3.Text)''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''Dim BQuerry As New BLL.BLL_QuerryCompositonDim BIsEmpty As StringBIsEmpty = BQuerry.isEmpty(UQuery)  '判断是否为空If BQuerry.QuerryOK = False Then    '如果判断失败，则退出Exit SubEnd IfDim BModifyFild As New Entity.Entity_QueryCompositonBModifyFild = BQuerry.ModifyFild(UQuery)    '将汉字转换为计算机能识别的语言Dim table As New DataTabletable = BQuerry.QuerryStuUp(BModifyFild)If table.Rows.Count <= 0 ThenMsgBox("没有记录")ElseFor i = 0 To table.Rows.Count - 1 '将dt表中的内容显示在DataGridView中  ’这种方式显示部分myGrid.Rows.Add()myGrid.Rows(i).Cells(0).Value = table.Rows(i)(0) '卡号  myGrid.Rows(i).Cells(1).Value = table.Rows(i)(1) '学号 myGrid.Rows(i).Cells(2).Value = table.Rows(i)(2) '学生姓名 myGrid.Rows(i).Cells(3).Value = table.Rows(i)(4) '性别myGrid.Rows(i).Cells(4).Value = table.Rows(i)(5) '上机日期myGrid.Rows(i).Cells(5).Value = table.Rows(i)(6) '上机时间myGrid.Rows(i).Cells(6).Value = table.Rows(i)(7) '下机日期myGrid.Rows(i).Cells(7).Value = table.Rows(i)(8) '下机时间myGrid.Rows(i).Cells(8).Value = table.Rows(i)(10) '消费金额'  myGrid.Rows(i).Cells(9).Value = table.Rows(i)(9) '操作员Next imyGrid.Rows(0).Selected = FalseEnd IfCatch ex As ExceptionMsgBox(ex.Message, vbOKOnly, "警告！")End TryEnd SubProtected Overrides Sub cmdOut_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)Dim grd = daochu(myGrid)End SubPrivate Sub FrmQuerryRecALLStuUP_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.LoadcobFild1.Items.Add("卡号")cobFild1.Items.Add("学号")cobFild1.Items.Add("姓名")cobFild1.Items.Add("性别")cobFild1.Items.Add("上机日期")cobFild1.Items.Add("上机时间")cobFild1.Items.Add("下机日期")cobFild1.Items.Add("下机时间")cobFild1.Items.Add("消费金额")cobFild2.Items.Add("卡号")cobFild2.Items.Add("学号")cobFild2.Items.Add("姓名")cobFild2.Items.Add("性别")cobFild2.Items.Add("上机日期")cobFild2.Items.Add("上机时间")cobFild2.Items.Add("下机日期")cobFild2.Items.Add("下机时间")cobFild2.Items.Add("消费金额")cobFild3.Items.Add("卡号")cobFild3.Items.Add("学号")cobFild3.Items.Add("姓名")cobFild3.Items.Add("性别")cobFild3.Items.Add("上机日期")cobFild3.Items.Add("上机时间")cobFild3.Items.Add("下机日期")cobFild3.Items.Add("下机时间")cobFild3.Items.Add("消费金额")End Sub
End Class

2、B层

'/*************************************************
'作者：金福林
'小组: 无
'说明：组合框B层
'创建日期：2014/5/5 20:10:13
'版本号：1.1.0
'**********************************************/ Public Class BLL_QuerryCompositonImplements IDAL.IDAL_QuerryCompositonPublic QuerryOK As Boolean = FalsePublic Function CombineString(ByVal QuerryCompositon As Entity.Entity_QueryCompositon) As StringEnd FunctionPublic Function isEmpty(ByVal QuerryCompositon As Entity.Entity_QueryCompositon) As StringIf QuerryCompositon.FiledName1 = "" ThenMsgBox("字段名不能为空，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.Operator1 = "" ThenMsgBox("操作符不能为空，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.QueryContent1 = "" ThenMsgBox("查询内容不能为空，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.QueryContent1.Length > 11 ThenMsgBox("您对查询内容一输入的字符串过长，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.Combine1 <> "" Then     '如果组合关系不为空If QuerryCompositon.FiledName2 = "" ThenMsgBox("当存在组合关系时，字段名不能为空，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.Operator2 = "" ThenMsgBox("当存在组合关系时，操作符不能为空，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.QueryContent2 = "" ThenMsgBox("当存在组合关系时，查询内容不能为空，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.QueryContent2.Length > 11 ThenMsgBox("您对查询内容二输入的字符串过长，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfEnd IfIf QuerryCompositon.Combine2 <> "" Then     '如果组合关系不为空If QuerryCompositon.FiledName3 = "" ThenMsgBox("当存在组合关系时，字段名不能为空，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.Operator3 = "" ThenMsgBox("当存在组合关系时，操作符不能为空，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.QueryContent3 = "" ThenMsgBox("当存在组合关系时，查询内容不能为空，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfIf QuerryCompositon.QueryContent2.Length > 11 ThenMsgBox("您对查询内容三输入的字符串过长，请重新输入", vbOKOnly, "警告！")Exit FunctionEnd IfEnd IfQuerryOK = TrueEnd FunctionPublic Function ModifyFild(ByVal QUerryCompositon As Entity.Entity_QueryCompositon) As Entity.Entity_QueryCompositonDim tempString As StringDim CombineString As New Entity.Entity_QueryCompositonSelect Case QUerryCompositon.FiledName1''''''''''''''学生信息维护的字段修改''''''''''''''''''''''''''Case "学号"tempString = "studentNo"Case "卡号"tempString = "cardno"Case "性别"tempString = "sex"Case "年级"tempString = "grade"Case "班级"tempString = "class"Case "姓名"tempString = "studentName"Case "余额"tempString = "cash"''''''''''''学生上机记录的字段更改'''''''''''''''''Case "上机日期"tempString = "ondate"Case "上机时间"tempString = "ontime"Case "下机日期"tempString = "offdate"Case "下机时间"tempString = "offtime"Case "消费金额"tempString = "consume"''''''''''''''操作员工作记录字段''''''''''''''''''''''Case "教师"tempString = "UserID"Case "级别"tempString = "Level"Case "注册日期"tempString = "LoginDate"Case "注册时间"tempString = "LoginTime"Case "注销日期"tempString = "LogoutDate"Case "注销时间"tempString = "LogoutTime"Case "机器名"tempString = "computer"Case ElsetempString = ""End SelectCombineString.FiledName1 = tempString   '修改第一个字符串的名称Select Case QUerryCompositon.FiledName2Case "学号"tempString = "studentNo"Case "卡号"tempString = "cardno"Case "性别"tempString = "sex"Case "年级"tempString = "grade"Case "班级"tempString = "class"Case "姓名"tempString = "studentName"Case "余额"tempString = "cash"''''''''''''学生上机记录的字段更改'''''''''''''''''Case "上机日期"tempString = "ondate"Case "上机时间"tempString = "ontime"Case "下机日期"tempString = "offdate"Case "下机时间"tempString = "offtime"Case "消费金额"tempString = "consume"''''''''''''''操作员工作记录字段''''''''''''''''''''''Case "教师"tempString = "UserID"Case "级别"tempString = "Level"Case "注册日期"tempString = "LoginDate"Case "注册时间"tempString = "LoginTime"Case "注销日期"tempString = "LogoutDate"Case "注销时间"tempString = "LogoutTime"Case "机器名"tempString = "computer"Case ElsetempString = ""End SelectCombineString.FiledName2 = tempStringSelect Case QUerryCompositon.FiledName3Case "学号"tempString = "studentNo"Case "卡号"tempString = "cardno"Case "性别"tempString = "sex"Case "年级"tempString = "grade"Case "班级"tempString = "class"Case "姓名"tempString = "studentName"Case "余额"tempString = "cash"''''''''''''学生上机记录的字段更改'''''''''''''''''Case "上机日期"tempString = "ondate"Case "上机时间"tempString = "ontime"Case "下机日期"tempString = "offdate"Case "下机时间"tempString = "offtime"Case "消费金额"tempString = "consume"''''''''''''''操作员工作记录字段''''''''''''''''''''''Case "教师"tempString = "UserID"Case "级别"tempString = "Level"Case "注册日期"tempString = "LoginDate"Case "注册时间"tempString = "LoginTime"Case "注销日期"tempString = "LogoutDate"Case "注销时间"tempString = "LogoutTime"Case "机器名"tempString = "computer"Case ElsetempString = ""End SelectCombineString.FiledName3 = tempStringSelect Case QUerryCompositon.Combine1Case "与"tempString = "and"Case "或"tempString = "or"Case ElsetempString = ""End SelectCombineString.Combine1 = tempStringSelect Case QUerryCompositon.Combine2Case "与"tempString = "and"Case "或"tempString = "or"Case ElsetempString = ""End SelectCombineString.Combine2 = tempString'Select Case QUerryCompositon.Operator1'    Case "="'        tempString = "like"'        CombineString.Operator1 = tempString'    Case Else'        tempString = ""'        CombineString.Operator1 = QUerryCompositon.Operator1'End Select'Select Case QUerryCompositon.Operator2'    Case "="'        tempString = "like"'        CombineString.Operator2 = tempString'    Case Else'        tempString = ""'        CombineString.Operator2 = QUerryCompositon.Operator2'End Select'Select Case QUerryCompositon.Operator3'    Case "="'        tempString = "like"'        CombineString.Operator3 = tempString'    Case Else'        tempString = ""'        CombineString.Operator3 = QUerryCompositon.Operator3'End Select'''''''将未替换的字符仍然保留为原来字符'''''''''''''''''''''''CombineString.QueryContent1 = QUerryCompositon.QueryContent1CombineString.QueryContent2 = QUerryCompositon.QueryContent2CombineString.QueryContent3 = QUerryCompositon.QueryContent3CombineString.Operator1 = QUerryCompositon.Operator1CombineString.Operator2 = QUerryCompositon.Operator2CombineString.Operator3 = QUerryCompositon.Operator3Return CombineStringEnd FunctionPublic Function QuerryOperator(ByVal QuerryCompositon As Entity.Entity_QueryCompositon) As System.Data.DataTable Implements IDAL.IDAL_QuerryCompositon.QuerryOperatorDim DQueryOperator As New DAL.DAL_QuerryCompositonDim table As New DataTabletable = DQueryOperator.QuerryOperator(QuerryCompositon)Return tableEnd FunctionPublic Function QuerryStuInfo(ByVal QuerryCompositon As Entity.Entity_QueryCompositon) As System.Data.DataTable Implements IDAL.IDAL_QuerryCompositon.QuerryStuInfoDim DQueryStu As New DAL.DAL_QuerryCompositonDim table As New DataTabletable = DQueryStu.QuerryStuInfo(QuerryCompositon)Return tableEnd FunctionPublic Function QuerryStuUp(ByVal QuerryCompositon As Entity.Entity_QueryCompositon) As System.Data.DataTable Implements IDAL.IDAL_QuerryCompositon.QuerryStuUpDim DQueryStuUP As New DAL.DAL_QuerryCompositonDim table As New DataTabletable = DQueryStuUP.QuerryStuUp(QuerryCompositon)Return tableEnd Function
End Class

3、D层

'/*************************************************
'作者：金福林
'小组: 无
'说明：组合查询D层
'创建日期：2014/5/5 21:02:58
'版本号：1.1.0
'**********************************************/ Public Class DAL_QuerryCompositonImplements IDAL.IDAL_QuerryCompositonPublic Function QuerryOperator(ByVal QuerryCompositon As Entity.Entity_QueryCompositon) As System.Data.DataTable Implements IDAL.IDAL_QuerryCompositon.QuerryOperatorDim strcon As StringDim sqlHelper As New SqlHelperIf QuerryCompositon.Combine1 = "" Then '如果第一个组合框为空strcon = "select * from worklog_Info where " & QuerryCompositon.FiledName1 & " " & QuerryCompositon.Operator1 _& "'" & QuerryCompositon.QueryContent1 & "'"ElseIf QuerryCompositon.Combine2 = "" Then  '如果第一个不为空，第二个组合框为空strcon = "select * from worklog_Info where " & QuerryCompositon.FiledName1 & " " & QuerryCompositon.Operator1 _& "'" & QuerryCompositon.QueryContent1 & "'  " & QuerryCompositon.Combine1 & "  " & QuerryCompositon.FiledName2 _& " " & QuerryCompositon.Operator2 & "'" & QuerryCompositon.QueryContent2 & "'"Else    '如果两个组合框都不为空strcon = "select * from worklog_Info where " & QuerryCompositon.FiledName1 & " " & QuerryCompositon.Operator1 _& "'" & QuerryCompositon.QueryContent1 & "' " & QuerryCompositon.Combine1 & "  " & QuerryCompositon.FiledName2 _& " " & QuerryCompositon.Operator2 & "'" & QuerryCompositon.QueryContent2 & "' " & QuerryCompositon.Combine2 _& "  " & QuerryCompositon.FiledName3 & " " & QuerryCompositon.Operator3 & "'" & QuerryCompositon.QueryContent3 & "'"End IfEnd IfReturn sqlHelper.ExecSelect(strcon, CommandType.Text)End FunctionPublic Function QuerryStuInfo(ByVal QuerryCompositon As Entity.Entity_QueryCompositon) As System.Data.DataTable Implements IDAL.IDAL_QuerryCompositon.QuerryStuInfoDim strcon As StringDim sqlHelper As New SqlHelperIf QuerryCompositon.Combine1 = "" Then '如果第一个组合框为空strcon = "select * from student_Info where " & QuerryCompositon.FiledName1 & "  " & QuerryCompositon.Operator1 _& "'" & QuerryCompositon.QueryContent1 & "'"ElseIf QuerryCompositon.Combine2 = "" Then  '如果第一个不为空，第二个组合框为空strcon = "select * from student_Info where " & QuerryCompositon.FiledName1 & "  " & QuerryCompositon.Operator1 _& "'" & QuerryCompositon.QueryContent1 & "'  " & QuerryCompositon.Combine1 & "  " & QuerryCompositon.FiledName2 _& "  " & QuerryCompositon.Operator2 & "'" & QuerryCompositon.QueryContent2 & "'"Else    '如果两个组合框都不为空strcon = "select * from student_Info where " & QuerryCompositon.FiledName1 & "  " & QuerryCompositon.Operator1 _& "'" & QuerryCompositon.QueryContent1 & "' " & QuerryCompositon.Combine1 & "  " & QuerryCompositon.FiledName2 _& "  " & QuerryCompositon.Operator2 & "'" & QuerryCompositon.QueryContent2 & "' " & QuerryCompositon.Combine2 _& "  " & QuerryCompositon.FiledName3 & "  " & QuerryCompositon.Operator3 & "'" & QuerryCompositon.QueryContent3 & "'"End IfEnd IfReturn sqlHelper.ExecSelect(strcon, CommandType.Text)End FunctionPublic Function QuerryStuUp(ByVal QuerryCompositon As Entity.Entity_QueryCompositon) As System.Data.DataTable Implements IDAL.IDAL_QuerryCompositon.QuerryStuUpDim strcon As StringDim sqlHelper As New SqlHelperIf QuerryCompositon.Combine1 = "" Then '如果第一个组合框为空strcon = "select * from Line_Info where " & QuerryCompositon.FiledName1 & "  " & QuerryCompositon.Operator1 _& "'" & QuerryCompositon.QueryContent1 & "'"ElseIf QuerryCompositon.Combine2 = "" Then  '如果第一个不为空，第二个组合框为空strcon = "select * from Line_Info where " & QuerryCompositon.FiledName1 & "  " & QuerryCompositon.Operator1 _& "'" & QuerryCompositon.QueryContent1 & "'  " & QuerryCompositon.Combine1 & "  " & QuerryCompositon.FiledName2 _& "  " & QuerryCompositon.Operator2 & "'" & QuerryCompositon.QueryContent2 & "'"Else    '如果两个组合框都不为空strcon = "select * from Line_Info where " & QuerryCompositon.FiledName1 & "  " & QuerryCompositon.Operator1 _& "'" & QuerryCompositon.QueryContent1 & "' " & QuerryCompositon.Combine1 & "  " & QuerryCompositon.FiledName2 _& "  " & QuerryCompositon.Operator2 & "'" & QuerryCompositon.QueryContent2 & "' " & QuerryCompositon.Combine2 _& "  " & QuerryCompositon.FiledName3 & "  " & QuerryCompositon.Operator3 & "'" & QuerryCompositon.QueryContent3 & "'"End IfEnd IfReturn sqlHelper.ExecSelect(strcon, CommandType.Text)End Function
End Class

4、实体层

'/*************************************************
'作者：金福林
'小组: 无
'说明：用于组合查询的类
'创建日期：2014/5/5 20:01:08
'版本号：1.1.0
'**********************************************/ Public Class Entity_QueryCompositonPrivate e_FiledName1 As String '字段1  Public Property FiledName1 As StringGetReturn Me.e_FiledName1End GetSet(ByVal value As String)Me.e_FiledName1 = valueEnd SetEnd PropertyPrivate e_FiledName2 As String '字段名2  Public Property FiledName2 As StringGetReturn Me.e_FiledName2End GetSet(ByVal value As String)Me.e_FiledName2 = valueEnd SetEnd PropertyPrivate e_FiledName3 As String '字段名3  Public Property FiledName3 As StringGetReturn Me.e_FiledName3End GetSet(ByVal value As String)Me.e_FiledName3 = valueEnd SetEnd PropertyPrivate e_Operator1 As String '操作符1  Public Property Operator1 As StringGetReturn Me.e_Operator1End GetSet(ByVal value As String)Me.e_Operator1 = valueEnd SetEnd PropertyPrivate e_Operator2 As String '操作符2  Public Property Operator2 As StringGetReturn Me.e_Operator2End GetSet(ByVal value As String)Me.e_Operator2 = valueEnd SetEnd PropertyPrivate e_Operator3 As String '操作符3  Public Property Operator3 As StringGetReturn Me.e_Operator3End GetSet(ByVal value As String)Me.e_Operator3 = valueEnd SetEnd PropertyPrivate e_QueryContent1 As String '查询内容1  Public Property QueryContent1 As StringGetReturn Me.e_QueryContent1End GetSet(ByVal value As String)Me.e_QueryContent1 = valueEnd SetEnd PropertyPrivate e_QueryContent2 As String '查询内容2  Public Property QueryContent2 As StringGetReturn Me.e_QueryContent2End GetSet(ByVal value As String)Me.e_QueryContent2 = valueEnd SetEnd PropertyPrivate e_QueryContent3 As String '查询内容3  Public Property QueryContent3 As StringGetReturn Me.e_QueryContent3End GetSet(ByVal value As String)Me.e_QueryContent3 = valueEnd SetEnd PropertyPrivate e_CompositionRelation1 As String '组合关系1  Public Property Combine1 As StringGetReturn Me.e_CompositionRelation1End GetSet(ByVal value As String)Me.e_CompositionRelation1 = valueEnd SetEnd PropertyPrivate e_CompositionRelation2 As String '组合关系2  Public Property Combine2 As StringGetReturn Me.e_CompositionRelation2End GetSet(ByVal value As String)Me.e_CompositionRelation2 = valueEnd SetEnd Property
End Class

5、接口层

Imports Entity
Public Interface IDAL_QuerryCompositon'  Function isEmpty(ByVal QuerryCompositon As Entity_QueryCompositon) As String' Function CombineString(ByVal QuerryCompositon As Entity_QueryCompositon) As String' Function ModifyFild(ByVal QUerryCompositon As Entity_QueryCompositon) As Entity_QueryCompositonFunction QuerryStuInfo(ByVal QuerryCompositon As Entity_QueryCompositon) As DataTableFunction QuerryStuUp(ByVal QuerryCompositon As Entity_QueryCompositon) As DataTableFunction QuerryOperator(ByVal QuerryCompositon As Entity_QueryCompositon) As DataTable
End Interface

6、sqlhelper类在我上篇博客中已经写到

http://blog.csdn.net/jinfulin/article/details/25072239

对于这么多代码，可能大家第一次看有点头大，大家主要看实体层和D层，不要照搬，领会思想，理解了之后就会觉得很简单了。