机房收费系统—组合查询
关于组合查询，真的是一个令人头疼的东西，但是当自己突然间的做出来时，却莫名的有种貌似又不是很难得感觉。昨天弄了整整一下午，今天的下午终于在调试了两个小时做出来了。
首先是查到了一些关于组合查询的博客，有一个共同的特点就是都要获得用户所选的字段名并转化成数据库表中的字段名，这样实现了人机共同语言的转换。但是代码实在是太复杂了，在小星星的引导下，我知道了可以定义模块的办法。最后我是采用了这样一种方法终于成功了。
定义在模块中的代码如下：
'将选择的字段汉字转化成数据库中的字段，——计算机语言
'因为以后还会有好多个组合查询的窗体，会用到下面的字段，一起都写出来，很方便调用
Public Function FieldName(strFieldName As String) As String
Select Case strFieldName
Case "卡号"
FieldName = "cardno"
Case "学号"
FieldName = "studentNo"
Case "姓名"
FieldName = "studentName"
Case "性别"
FieldName = "sex"
Case "系别"
FieldName = "department"
Case "年级"
FieldName = "grade"
Case "班号"
FieldName = "class"
Case "上机日期"
FieldName = "ondate"
Case "上机时间"
FieldName = "ontime"
Case "下机日期"
FieldName = "offdate"
Case "下机时间"
FieldName = "offtime"
Case "消费金额"
FieldName = "consume"
Case "余额"
FieldName = "cash"
Case "备注"
FieldName = "status"
Case "教师"
FieldName = "Level"
Case "注册日期"
FieldName = "LoginDate"
Case "注册时间"
FieldName = "LoginTime"
Case "注销日期"
FieldName = "LogoutDate"
Case "注销时间"
FieldName = "LogoutTime"
Case "机器名"
FieldName = "computer"
End Select
End Function
'将操作符转化成数据库表中的字段名
Public Function Operate(strOperate As String)
Select Case strOperate
Case "="
Operate = "="
Case "<"
Operate = "<"
Case ">"
Operate = ">"
Case "<>"
Operate = "<>"
End Select
End Function
'将连接符转化成数据库表中的字段名
Public Function Connect(strConnect As String) As String
Select Case strConnect
Case "或"
Connect = "or"
Case "与"
Connect = "and"
Case ""
Connect = ""
End Select
End Function
学生基本信息维护窗体
Private Sub cmdInquire_Click()
Dim objrs As ADODB.Recordset
Dim txtSQL As String
Dim msgText As String
Dim strA As String '定义三个保存SQL语句的字符串
Dim strB As String
Dim strC As String
'先写上一个不完整的SQL语句，等用到时再补充
txtSQL = "select * from student_Info where "
'每个字符串代表分别是三行三种查询条件时的三种情况
strA = FieldName(cmbField(0).Text) & Operate(cmbOperate(0).Text) & Trim(txtContent(0).Text)
strB = strA & " " & Connect(cmbConnect(0).Text) & " " & FieldName(cmbField(1).Text) & Operate(cmbOperate(1).Text) & Trim(txtContent(1).Text)
strC = strB & " " & Connect(cmbConnect(1).Text) & " " & FieldName(cmbField(2).Text) & Operate(cmbOperate(2).Text) & Trim(txtContent(2).Text)
'判断查询条件，当只有一行条件时，默认选择第一行的查询条件，即第一个组合关系没有选择；
'当有两条查询条件时，默认是选择前两行，即第一个组合关系不为空
'当有三行查询条件时，即每个控件都不为空，即第二个组合关系不为空
If Trim(cmbConnect(0).Text) = "" Then
If Trim(cmbField(0).Text) = "" Or Trim(cmbOperate(0).Text) = "" Or (txtContent(0).Text) = "" Then
MsgBox "请在第一行输入查询条件", 48, "提示"
Exit Sub
Else
txtSQL = txtSQL & strA
End If
Else
If Trim(cmbConnect(1).Text) = "" Then
If Trim(cmbField(1).Text) = "" Or Trim(cmbOperate(1).Text) = "" Or (txtContent(1).Text) = "" Then
MsgBox "请在第二行输入查询条件", 48, "提示"
Exit Sub
Else
txtSQL = txtSQL & strB
End If
Else
If Trim(cmbField(2).Text) = "" Or Trim(cmbOperate(2).Text) = "" Or (txtContent(2).Text) = "" Then
MsgBox "请在第三行输入查询条件", 48, "提示"
Exit Sub
Else
txtSQL = txtSQL & strC
End If
End If
End If
Set objrs = ExecuteSQL(txtSQL, msgText)
If objrs.EOF Then
MsgBox "没有查到记录", 48, "提示"
Exit Sub
End If
'将查询到的数据写到myFlexGrid表格中，在写入数据之前要注意清空数据表，防止数据重复
With myFlexGrid
.Clear
.Cols = 7
.CellAlignment = 4
.TextMatrix(0, 0) = "卡号"
.TextMatrix(0, 1) = "学号"
.TextMatrix(0, 2) = "姓名"
.TextMatrix(0, 3) = "性别"
.TextMatrix(0, 4) = "系别"
.TextMatrix(0, 5) = "年级"
.TextMatrix(0, 6) = "班级"
.Rows = 1
Do While Not objrs.EOF
.Rows = .Rows + 1
.CellAlignment = 4
.TextMatrix(.Rows - 1, 0) = objrs!cardno
.TextMatrix(.Rows - 1, 1) = objrs!studentNo
.TextMatrix(.Rows - 1, 2) = objrs!studentName
.TextMatrix(.Rows - 1, 3) = objrs!sex
.TextMatrix(.Rows - 1, 4) = objrs!department
.TextMatrix(.Rows - 1, 5) = objrs!grade
.TextMatrix(.Rows - 1, 6) = objrs!Class
objrs.MoveNext
Loop
End With
objrs.Close
End Sub