机房收费系统之组合查询

       组合查询其实就是多个查询条件的限定，只要思路清晰了，执行起来便容易多了。首先我把这三个查询条件看作三个整体，定义了三个过程，并将combo的字段转换成数据库中对应的字段名，执行语句时直接调用，这样在查询过程中就减少了代码量。

比如定义第一查询条件：

Private Sub InquireCondition1()       '定义第一查询条件过程，将combo的字段名转换成数据库对应的字段名   Select Case Combo1       Case "卡号"          Ziduan(0) = "cardNo"       Case "学号"          Ziduan(0) = "studentNo"       Case "姓名"          Ziduan(0) = "studentName"       Case "性别"          Ziduan(0) = "sex"       Case "系别"          Ziduan(0) = "Department"       Case "年级"          Ziduan(0) = "grade"       Case "班号"          Ziduan(0) = "class"           End Select            Select Case Combo7       Case "与"          ZuheRelation(0) = "and"       Case "或"          ZuheRelation(0) = "or"   End SelectEnd Sub

然后在查询中编写代码如下：

 Dim msgText As String                 '将sql语句定义为一个过程，在查询事件中直接引用   txtSQL = "select * from Line_Info where  "         If Combo1.Text = "" Then     '判断字段名是否为空     MsgBox "请选择字段名！", vbOKOnly + vbExclamation, "警告"     Combo1.SetFocus     Exit Sub  End If    If Combo4.Text = "" Then      '判断选择符是否为空     MsgBox "请选择操作符！", vbOKOnly + vbExclamation, "警告"     Combo4.SetFocus     Exit Sub  End If    If Text1.Text = "" Then         '判断查询内容是否为空     MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation, "警告"     Text1.SetFocus     Exit Sub  End If      Call InquireCondition1                If Combo7.Text = "" Then         '执行第一查询条件       txtSQL = txtSQL & " " & Trim(Ziduan(0)) & "" & Trim(Combo4.Text) & "'" & Trim(Text1.Text) & "'"    Else                             '执行第一查询条件和第二查询条件             If Combo2.Text = "" Then                MsgBox "请选择字段名！", vbOKOnly + vbExclamation, "警告"                Combo2.SetFocus                Exit Sub             End If                      If Combo5.Text = "" Then                 MsgBox "请选择操作符！", vbOKOnly + vbExclamation, "警告"                 Combo5.SetFocus                 Exit Sub              End If                            If Text2.Text = "" Then                 MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation, "警告"                 Text2.SetFocus                 Exit Sub              End If                   Call InquireCondition2                         If Combo8.Text = "" Then                txtSQL = txtSQL & "" & Trim(Ziduan(0)) & "" & Trim(Combo4.Text) & "'" & Trim(Text1.Text) & "'" & " " & Trim(ZuheRelation(0)) & "   " & Trim(Ziduan(1)) & " " & Trim(Combo5.Text) & "'" & Trim(Text2.Text) & "'"             Else             '三个条件同时执行                      If Combo3.Text = "" Then                       MsgBox "请选择字段名！", vbOKOnly + vbExclamation, "警告"                       Combo3.SetFocus                       Exit Sub                      End If                                    If Combo6.Text = "" Then                        MsgBox "请选择操作符！", vbOKOnly + vbExclamation, "警告"                        Combo6.SetFocus                        Exit Sub                     End If                                          If Text3.Text = "" Then                        MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation, "警告"                        Text3.SetFocus                        Exit Sub                     End If                                          Call InquireCondition3                              txtSQL = txtSQL & "" & Trim(Ziduan(0)) & "" & Trim(Combo4.Text) & "'" & Trim(Text1.Text) & "'" & "" & Trim(ZuheRelation(0)) & "  " & Trim(Ziduan(1)) & "" & Trim(Combo5.Text) & "'" & Trim(Text2.Text) & "'" & "" & Trim(ZuheRelation(1)) & "  " & Trim(Ziduan(2)) & "" & Trim(Combo6.Text) & "'" & Trim(Text3.Text) & "'"            End If     End If

这样便可以顺利实现了。