【机房收费系统】组合查询
终于做到组合查询这里了，而且我也掌握了它的方法，根据帅博客改编：
组合查询也不是那么难，之前看到别人总说这个话题，自己就先给它定位了，很难，现在看来真的不能给自己下定位，不能给自己没有接触过的东西随便下定义，就像小马过河的故事！
我来说说我的成长经历：
首先，我先自己想了一个办法，代码如下：
txtSQL = "select * from line_info where "
If Combo3.Text = "卡号" Then
'判断操作符和查询的内容是否为空
If Trim(Combo6.Text) = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation
Combo6.SetFocus
Exit Sub
ElseIf Trim(Text3.Text) = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation
Text3.SetFocus
Exit Sub
ElseIf Not IsNumeric(Trim(Text3.Text)) Then
MsgBox "请输入数字！"
Exit Sub
'如果不为空的话，看是否为”=“
ElseIf Combo6.Text = "=" Then
'调出数据库中为=号的字段
txtSQL = txtSQL & "cardno='" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = "<" Then
txtSQL = txtSQL & "cardno<'" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = ">" Then
txtSQL = txtSQL & "cardno>'" & Trim(Text3.Text) & "'"
'这时，就剩下一个《》了
Else
txtSQL = txtSQL & "cardno<>'" & Trim(Text3.Text) & "'"
End If
ElseIf Combo3.Text = "姓名" Then
'判断操作符和查询的内容是否为空
If Trim(Combo6.Text) = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation
Combo6.SetFocus
Exit Sub
ElseIf Trim(Text3.Text) = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation
Text3.SetFocus
Exit Sub
'如果不为空的话，看是否为”=“
ElseIf Combo6.Text = "=" Then
'调出数据库中为=号的字段
txtSQL = txtSQL & "studentname='" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = "<" Then
txtSQL = txtSQL & "studentname<'" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = ">" Then
txtSQL = txtSQL & "studentname>'" & Trim(Text3.Text) & "'"
'这时，就剩下一个《》了
Else
txtSQL = txtSQL & "student<>'" & Trim(Text3.Text) & "'"
End If
ElseIf Combo3.Text = "上机日期" Then
'判断操作符和查询的内容是否为空
If Trim(Combo6.Text) = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation
Combo6.SetFocus
Exit Sub
ElseIf Trim(Text3.Text) = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation
Text3.SetFocus
Exit Sub
ElseIf Not IsDate(Text3.Text) Then
MsgBox "请输入正确的日期类型！(yyyy-mm-dd)"
Text3.SetFocus
Exit Sub
Text3.Text = Format(Text3.Text, "yyyy-mm-dd")
'如果不为空的话，看是否为”=“
ElseIf Combo6.Text = "=" Then
'调出数据库中为=号的字段
txtSQL = txtSQL & "ondate='" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = "<" Then
txtSQL = txtSQL & "ondate<'" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = ">" Then
txtSQL = txtSQL & "ondate>'" & Trim(Text3.Text) & "'"
'这时，就剩下一个《》了
Else
txtSQL = txtSQL & "ondate<>'" & Trim(Text3.Text) & "'"
End If
ElseIf Combo3.Text = "上机时间" Then
'判断操作符和查询的内容是否为空
If Trim(Combo6.Text) = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation
Combo6.SetFocus
Exit Sub
ElseIf Trim(Text3.Text) = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation
Text3.SetFocus
Exit Sub
ElseIf Not IsDate(Text3.Text) Then
MsgBox "请输入正确的时间类型！(00:00:00)"
Text3.SetFocus
Exit Sub
Text3.Text = Format(Text3.Text, "00:00:00")
'如果不为空的话，看是否为”=“
ElseIf Combo6.Text = "=" Then
'调出数据库中为=号的字段
txtSQL = txtSQL & "ontime='" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = "<" Then
txtSQL = txtSQL & "ontime<'" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = ">" Then
txtSQL = txtSQL & "ontime>'" & Trim(Text3.Text) & "'"
'这时，就剩下一个《》了
Else
txtSQL = txtSQL & "ontime<>'" & Trim(Text3.Text) & "'"
End If
ElseIf Combo3.Text = "下机日期" Then
'判断操作符和查询的内容是否为空
If Trim(Combo6.Text) = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation
Combo6.SetFocus
Exit Sub
ElseIf Trim(Text3.Text) = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation
Text3.SetFocus
Exit Sub
ElseIf Not IsDate(Text3.Text) Then
MsgBox "请输入正确的日期类型！(yyyy-mm-dd)"
Text3.SetFocus
Exit Sub
Text3.Text = Format(Text3.Text, "yyyy-mm-dd")
'如果不为空的话，看是否为”=“
ElseIf Combo6.Text = "=" Then
'调出数据库中为=号的字段
txtSQL = txtSQL & "offdate='" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = "<" Then
txtSQL = txtSQL & "offdate<'" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = ">" Then
txtSQL = txtSQL & "offdate>'" & Trim(Text3.Text) & "'"
'这时，就剩下一个《》了
Else
txtSQL = txtSQL & "offdate<>'" & Trim(Text3.Text) & "'"
End If
ElseIf Combo3.Text = "下机时间" Then
'判断操作符和查询的内容是否为空
If Trim(Combo6.Text) = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation
Combo6.SetFocus
Exit Sub
ElseIf Trim(Text3.Text) = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation
Text3.SetFocus
Exit Sub
ElseIf Not IsDate(Text3.Text) Then
MsgBox "请输入正确的时间类型！(00:00:00)"
Text3.SetFocus
Exit Sub
Text3.Text = Format(Text3.Text, "00:00:00")
'如果不为空的话，看是否为”=“
ElseIf Combo6.Text = "=" Then
'调出数据库中为=号的字段
txtSQL = txtSQL & "offtime='" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = "<" Then
txtSQL = txtSQL & "offtime<'" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = ">" Then
txtSQL = txtSQL & "offtime>'" & Trim(Text3.Text) & "'"
'这时，就剩下一个《》了
Else
txtSQL = txtSQL & "offtime<>'" & Trim(Text3.Text) & "'"
End If
ElseIf Combo3.Text = "消费金额" Then
'判断操作符和查询的内容是否为空
If Trim(Combo6.Text) = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation
Combo6.SetFocus
Exit Sub
ElseIf Trim(Text3.Text) = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation
Text3.SetFocus
Exit Sub
ElseIf Not IsNumeric(Trim(Text3.Text)) Then
MsgBox "请输入数字！"
Text3.SetFocus
Exit Sub
'如果不为空的话，看是否为”=“
ElseIf Combo6.Text = "=" Then
'调出数据库中为=号的字段
txtSQL = txtSQL & "cash='" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = "<" Then
txtSQL = txtSQL & "cash<'" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = ">" Then
txtSQL = txtSQL & "cash>'" & Trim(Text3.Text) & "'"
'这时，就剩下一个《》了
Else
txtSQL = txtSQL & "cash<>'" & Trim(Text3.Text) & "'"
End If
ElseIf Combo3.Text = "余额" Then
'判断操作符和查询的内容是否为空
If Trim(Combo6.Text) = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation
Combo6.SetFocus
Exit Sub
ElseIf Trim(Text3.Text) = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation
Text3.SetFocus
Exit Sub
ElseIf Not IsNumeric(Trim(Text3.Text)) Then
MsgBox "请输入数字！"
Text3.SetFocus
Exit Sub
'如果不为空的话，看是否为”=“
ElseIf Combo6.Text = "=" Then
'调出数据库中为=号的字段
txtSQL = txtSQL & "cash='" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = "<" Then
txtSQL = txtSQL & "cash<'" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = ">" Then
txtSQL = txtSQL & "cash>'" & Trim(Text3.Text) & "'"
'这时，就剩下一个《》了
Else
txtSQL = txtSQL & "cash<>'" & Trim(Text3.Text) & "'"
End If
Else '这样在这里就是“备注”的代码了
'判断操作符和查询的内容是否为空
If Trim(Combo6.Text) = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation
Combo6.SetFocus
Exit Sub
ElseIf Trim(Text3.Text) = "" Then
MsgBox "请输入备注的电脑名称！", vbOKOnly + vbExclamation
Text3.SetFocus
Exit Sub
'如果不为空的话，看是否为”=“
ElseIf Combo6.Text = "=" Then
'调出数据库中为=号的字段
txtSQL = txtSQL & "computer='" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = "<" Then
txtSQL = txtSQL & "computer<'" & Trim(Text3.Text) & "'"
'同理，如果不是“=”，看是否为“<”
ElseIf Combo6.Text = ">" Then
txtSQL = txtSQL & "computer>'" & Trim(Text3.Text) & "'"
'这时，就剩下一个《》了
Else
txtSQL = txtSQL & "computer<>'" & Trim(Text3.Text) & "'"
End If '判断操作符和查询的内容是否为空
End If
这个看起来很复杂吧，没错，我忽略了计算机的能力，没有让它给我做工（赋值，循环的改变数据）。
我放弃了这个思路，决定参考别人的做法：
Private Sub Command2_Click()
If Combo1.Text = "" Or Combo4.Text = "" Or Text1.Text = "" Then
MsgBox "请输入正确的查询内容！"
Exit Sub
End If
txtSQL = "select * from line_info where " '这叫模糊查询
If Combo7.Text = "" And Combo8.Text = "" Then
'这是查询的第一行
txtSQL = txtSQL & field(Combo1.Text) & Trim(Combo4.Text) & "'" & Text1.Text & "'"
ElseIf Combo7.Text <> "" And Combo8.Text = "" Then
If Combo2.Text = "" Or Combo4.Text = "" Or Text2.Text = "" Then
MsgBox "请输入正确的查询方式！"
Exit Sub
End If
'先查第一行，在它的基础上再进行and or 第二行
txtSQL = txtSQL & field(Combo1.Text) & Trim(Combo4.Text) & "'" & Text1.Text & "'"
'查询第二行
txtSQL = txtSQL & field(Combo7.Text) & " " & field(Combo2.Text) & Trim(Combo5.Text) & "'" & Text2.Text & "'"
ElseIf Combo7.Text = "" And Combo8.Text <> "" Then
If Combo3.Text = "" Or Combo5.Text = "" Or Text3.Text = "" Then
MsgBox "请输入正确的查询方式！"
Exit Sub
End If
'查询第一行
txtSQL = txtSQL & field(Combo1.Text) & Trim(Combo4.Text) & "'" & Text1.Text & "'"
'查询第三行
txtSQL = txtSQL & field(Combo8.Text) & " " & field(Combo3.Text) & Trim(Combo6.Text) & "'" & Text3.Text & "'"
Else
If Combo2.Text = "" Or Combo4.Text = "" Or Text2.Text = "" Or Combo3.Text = "" Or Combo5.Text = "" Or Text3.Text = "" Then
MsgBox "请输入正确的查询方式！"
Exit Sub
End If
'三行都写下来
txtSQL = txtSQL & field(Combo1.Text) & Trim(Combo4.Text) & "'" & Text1.Text & "'"
txtSQL = txtSQL & field(Combo7.Text) & " " & field(Combo2.Text) & Trim(Combo5.Text) & "'" & Text2.Text & "'"
txtSQL = txtSQL & field(Combo8.Text) & " " & field(Combo3.Text) & Trim(Combo6.Text) & "'" & Text3.Text & "'"
End If
Set mrc = ExecuteSQL(txtSQL, msgText)
With myflexgrid
.Rows = 2
.CellAlignment = 4
.TextMatrix(1, 0) = "卡号"
.TextMatrix(1, 1) = "学号"
.TextMatrix(1, 2) = "学生姓名"
.TextMatrix(1, 3) = "系别"
.TextMatrix(1, 4) = "性别"
.TextMatrix(1, 5) = "上机日期"
.TextMatrix(1, 6) = "上机时间"
.TextMatrix(1, 7) = "下机日期"
.TextMatrix(1, 8) = "下机时间"
.TextMatrix(1, 9) = "上机时间"
.TextMatrix(1, 10) = "花费金额"
.TextMatrix(1, 11) = "状态"
.TextMatrix(1, 12) = "机器名"
Do While Not mrc.EOF
.Rows = .Rows + 1
.CellAlignment = 4
.TextMatrix(.Rows - 1, 0) = mrc.Fields(1)
.TextMatrix(.Rows - 1, 1) = mrc.Fields(2)
.TextMatrix(.Rows - 1, 2) = mrc.Fields(3)
.TextMatrix(.Rows - 1, 3) = mrc.Fields(4)
.TextMatrix(.Rows - 1, 4) = mrc.Fields(5)
.TextMatrix(.Rows - 1, 5) = mrc.Fields(6)
.TextMatrix(.Rows - 1, 6) = mrc.Fields(7)
.TextMatrix(.Rows - 1, 7) = mrc.Fields(8)
.TextMatrix(.Rows - 1, 8) = mrc.Fields(9)
.TextMatrix(.Rows - 1, 9) = mrc.Fields(10)
.TextMatrix(.Rows - 1, 10) = mrc.Fields(12)
.TextMatrix(.Rows - 1, 11) = mrc.Fields(13)
.TextMatrix(.Rows - 1, 12) = mrc.Fields(14)
mrc.MoveNext
Loop
End With
mrc.Close
End Sub
这个看起来就简单多了吧，这里用到了select的查找替换的功能，在这里，我还学会了怎么定义一个自己的过程：
Public Function field(name As String) As String
Select Case name
Case "卡号"
field = "cardno"
Case "姓名"
field = "studentname"
Case "上机日期"
field = "ondate"
Case "上机时间"
field = "ontime"
Case "下机日期"
field = "offdate"
Case "下机时间"
field = "offtime"
Case "消费金额"
field = "cash"
Case "机器名"
field = "computer"
Case "与"
field = "and"
Case "或"
field = "or"
End Select
End Function
这里，其中的name 可以随便写，它不参与别的代码的书写，只在这里出现，专门给field赋值用的。
这样，用一个function 和click事件下的代码，就可以简单的实现了！
ps:上面所用到的“”和‘’一定要看仔细！