基础很重要，查询如何“组合”！谈谈组合查询
前言：
在之前是没有接触过组合查询的。一听说，哇！组合查询！什么？没有听过，第一个反应。不会，哇塞，肯定好难。听别人的一说，哦！更加明白了，我做不出来！呵呵，这样一个心态。我开始了“组合”查询。后来当然是完成了，但我发现事情远远没有做完那么简单！
首先，还是先说说这些组合查询吧！
如下图，红色框的内容利用蓝色框的关系与下面黄色框的内容结合。进而来返回表中的数据
利用数组做为每个字段名的变量，这个问题就迎刃而解了。请看如下代码
第一部分：使文本框合法输入，并利用变量将字段内容取出来
Dim mrc As ADODB.Recordset
Dim strSQL As String
Dim strMsgtext As String
Dim Field(2) As String
Dim Operator(2) As String
Dim Logic(1) As String
MyFlexGrid.Clear
'确保输入条件合法
If Combo1.Text = "" Then
MsgBox "请输入字段名！", vbOKOnly + vbExclamation, "温馨提示！"
Combo1.SetFocus
Exit Sub
Else
Select Case Combo1.ListIndex
Case 0
Field(0) = "cardno"
Case 1
Field(0) = "name"
Case 2
Field(0) = "onlinetime"
Case 3
Field(0) = "onlinedate"
End Select
End If
If Combo4.Text = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation, "温馨提示！"
Combo4.SetFocus
Exit Sub
Else
Select Case Combo4.ListIndex
Case 0
Operator(0) = "<"
Case 1
Operator(0) = ">"
Case 2
Operator(0) = "="
Case 3
Operator(0) = "<>"
End Select
If Txtworda.Text = "" Then
MsgBox "请输入要查询的内容1!", vbOKOnly + vbExclamation, "温馨提示！"
Txtworda.SetFocus
Exit Sub
End If
End If
If Combo7.Text <> "" = True Then
'指定第一个逻辑字符
Select Case Combo7.ListIndex
Case 0
Logic(0) = "and"
Case 1
Logic(0) = "or"
End Select
If Combo2.Text = "" Then
MsgBox "请输入字段名！", vbOKOnly + vbExclamation, "温馨提示！"
Combo2.SetFocus
Exit Sub
Else
'指定第二个字段名字符
Select Case Combo2.ListIndex
Case 0
Field(1) = "cardno"
Case 1
Field(1) = "name"
Case 2
Field(1) = "onlinetime"
Case 3
Field(1) = "onlinedate"
End Select
If Combo5.Text = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation, "温馨提示！"
Combo5.SetFocus
Exit Sub
Else
'指定第二个关系运算符字符
Select Case Combo5.ListIndex
Case 0
Operator(1) = "<"
Case 1
Operator(1) = ">"
Case 2
Operator(1) = "="
Case 3
Operator(1) = "<>"
End Select
If Txtwordb.Text = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation, "温馨提示！"
Txtwordb.SetFocus
Exit Sub
End If
End If
End If
End If
If Combo8.Text <> "" = True Then
'指定第二个逻辑符字符串
Select Case Combo8.ListIndex
Case 0
Logic(1) = "and"
Case 1
Logic(1) = "or"
End Select
If Combo3.Text = "" Then
MsgBox "字段名！", vbOKOnly + vbExclamation, "温馨提示！"
Combo3.SetFocus
Exit Sub
Else
'指定第三个字段字符串
Select Case Combo3.ListIndex
Case 0
Field(2) = "cardno"
Case 1
Field(2) = "name"
Case 2
Field(2) = "onlinetime"
Case 3
Field(2) = "onlinedate"
End Select
If Combo6.Text = "" Then
MsgBox "请输入操作符！", vbOKOnly + vbExclamation, "温馨提示！"
Combo6.SetFocus
Exit Sub
Else
'指定第三个关系运算符字符串
Select Case Combo6.ListIndex
Case 0
Operator(2) = "<"
Case 1
Operator(2) = ">"
Case 2
Operator(2) = "="
Case 3
Operator(2) = "<>"
End Select
If Txtwordc.Text = "" Then
MsgBox "请输入要查询的内容！", vbOKOnly + vbExclamation, "温馨提示！"
Txtwordc.SetFocus
Exit Sub
End If
End If
End If
End If
这段代码的核心应该就一点
1.数组和select语句运用，来返回文本框查询内容
第二部分：判断逻辑符之间关系，执行sql 语句
'当第一个逻辑关系为空时，执行下面语句
If Combo7.Text = "" Then
strSQL = "select * from offlineinfo where" & " " & Field(0) & "" & Operator(0) & " '" & Txtworda.Text & "'"
Set mrc = ExecuteSQL(strSQL, strMsgtext)
With MyFlexGrid
Do While Not mrc.EOF
.TextMatrix(0, 0) = "卡号"
.TextMatrix(0, 1) = "姓名"
.TextMatrix(0, 2) = "上机日期"
.TextMatrix(0, 3) = "上机时间"
.ColWidth(1) = 1000
.ColWidth(0) = 1000
.ColWidth(2) = 1000
.ColWidth(3) = 1000
.Rows = .Rows + 1
.CellAlignment = 4
.TextMatrix(.Rows - 1, 0) = Trim(mrc.Fields(0))
.TextMatrix(.Rows - 1, 1) = Trim(mrc.Fields(4))
.TextMatrix(.Rows - 1, 2) = Trim(mrc.Fields(6))
.TextMatrix(.Rows - 1, 3) = Trim(mrc.Fields(7))
mrc.MoveNext
Loop
End With
Else
If Combo8.Text = "" Then
strSQL = "select * from offlineinfo where" & " " & Field(0) & " " & Operator(0) & " '" & Txtworda.Text & "' " & Logic(0) & " " & Field(1) & " " & Operator(1) & "'" & Txtwordb.Text & "'"
Set mrc = ExecuteSQL(strSQL, strMsgtext)
With MyFlexGrid
Do While Not mrc.EOF
.TextMatrix(0, 0) = "卡号"
.TextMatrix(0, 1) = "姓名"
.TextMatrix(0, 2) = "上机日期"
.TextMatrix(0, 3) = "上机时间"
.ColWidth(1) = 1000
.ColWidth(0) = 1000
.ColWidth(2) = 1000
.ColWidth(3) = 1000
.Rows = .Rows + 1
.CellAlignment = 4
.TextMatrix(.Rows - 1, 0) = Trim(mrc.Fields(0))
.TextMatrix(.Rows - 1, 1) = Trim(mrc.Fields(4))
.TextMatrix(.Rows - 1, 2) = Trim(mrc.Fields(6))
.TextMatrix(.Rows - 1, 3) = Trim(mrc.Fields(7))
mrc.MoveNext
Loop
End With
End If
If Combo8.Text <> "" Then
strSQL = "select * from offlineinfo where" & " " & Field(0) & " " & Operator(0) & " " & Txtworda.Text & " " & Logic(0) & " " & Field(1) & " " & Operator(1) & " '" & Txtwordb.Text & "' " & Logic(1) & " " & Field(2) & " " & Operator(2) & " '" & Txtwordc.Text & "'"
Set mrc = ExecuteSQL(strSQL, strMsgtext)
If mrc.BOF And mrc.EOF Then
MsgBox "没有该条记录！", vbOKOnly + vbExclamation, "温馨提示！"
End
End If
With MyFlexGrid
Do While Not mrc.EOF
.TextMatrix(0, 0) = "卡号"
.TextMatrix(0, 1) = "姓名"
.TextMatrix(0, 2) = "上机日期"
.TextMatrix(0, 3) = "上机时间"
.ColWidth(1) = 1000
.ColWidth(0) = 1000
.ColWidth(2) = 1000
.ColWidth(3) = 1000
.Rows = .Rows + 1
.CellAlignment = 4
.TextMatrix(.Rows - 1, 0) = Trim(mrc.Fields(0))
.TextMatrix(.Rows - 1, 1) = Trim(mrc.Fields(4))
.TextMatrix(.Rows - 1, 2) = Trim(mrc.Fields(6))
.TextMatrix(.Rows - 1, 3) = Trim(mrc.Fields(7))
mrc.MoveNext
Loop
End With
End If
End If
End Sub
这段代码的核心应该是这三句sql语句了。
总结：
组合查询就是这样。没有我传闻那样骇闻，也没有我想象中如此不能为之。仔细一想，首先还是自己把自己困住了。给了自己一个不会的理由，然后我很“淡定”的磨了很多天。其实这里面，我认为最为精到还是那几个数组的应用。看来还是基础工作没有做透啊！以前的债啊，还好现在“还回来了”！keep moving