機房收費系統——組合查詢
前言：組合查詢的實現用了三天時間，剛開始看這個窗體確實有點難度，開始鑽研原版的系統多點點會發現規律，與學生的查詢思路相似，所以多去實踐，錯了也沒有關係
以學生基本資訊維護為例
邏輯思路：組合查詢即為多條件查詢（查詢語句where後即為條件，全部在此做文章）窗體中最多是三個條件，兩個及兩個以上即為組合查詢。用的是學生查詢中語句拼接，以一個組合關係為節點判斷是否為組合查詢，如果是將這兩個條件組合起來即可，下面看
流程圖：
依據流程圖敲程式碼即可
自定義函式：
Public Function Field(i As String) As String
Select Case i
Case "與"
Field = "and"
Case "或"
Field = "or"
Case "卡號"
Field = "cardno"
Case "姓名"
Field = "studentname"
Case "學號"
Field = "studentno"
Case "系別"
Field = "department"
Case "年級"
Field = "grade"
Case "班級"
Field = "class"
Case "性別"
Field = "sex"
End Select
End Function
實現功能：將資料內容轉化為where子句可識別的資料表中的欄位名，方便呼叫
新增資料：
Dim a, b, c
For a = 0 To 2
With Combo1(a)
.AddItem "卡號"
.AddItem "學號"
.AddItem "姓名"
.AddItem "性別"
.AddItem "系別"
.AddItem "年級"
.AddItem "班級"
End With
Next a
For b = 0 To 2
With Combo2(b)
.AddItem "="
.AddItem "<"
.AddItem ">"
.AddItem "<>"
End With
Next b
For c = 0 To 1
With Combo3(c)
.AddItem "與"
.AddItem "或"
End With
Next c
功能：利用陣列控制元件新增內容，減少程式碼量
查詢程式碼如下：
stuSQL = "select * from student_info where " '查詢基本的條件
If Combo1(0).Text = "" Or Combo2(0).Text = "" Or Text1.Text = "" Then '判斷第一行資料是否為空
MsgBox "請輸入內容", 0 + 48, "提示"
Else
stuSQL = stuSQL & Field(Combo1(0).Text) & Combo2(0).Text & "'" & Text1.Text & "'" '查詢語句加上第一行資料條件
End If
'通過第一個組合關係框判斷是否是組合查詢
If Combo3(0).Text <> "" Then
If Combo1(1).Text = "" Or Combo2(1).Text = "" Or Text2.Text = "" Then '新增第二行資料
MsgBox "請輸入內容", 0 + 48, "提示"
Else
Select Case Combo3(0).Text
Case "與"
stuSQL = stuSQL & " and " & Field(Combo1(1).Text) & Combo2(1).Text & "'" & Text2.Text & "'" '組合關係條件確定
Case "或"
stuSQL = stuSQL & " or " & Field(Combo1(1).Text) & Combo2(1).Text & "'" & Text2.Text & "'"
End Select
End If
End If
'通過第二個組合關係框判斷是否是組合查詢
If Combo3(1).Text <> "" Then
If Combo1(2).Text = "" Or Combo2(2).Text = "" Or Text3.Text = "" Then '新增第三行資料
MsgBox "請輸入內容", 0 + 48, "提示"
Else
Select Case Combo3(1).Text
Case "與"
stuSQL = stuSQL & " and " & Field(Combo1(1).Text) & Combo2(1).Text & "'" & Text2.Text & "'"
Case "或"
stuSQL = stuSQL & " or " & Field(Combo1(1).Text) & Combo2(1).Text & "'" & Text2.Text & "'"
End Select
End If
End If
Set stumrc = ExecuteSQL(stuSQL, stuText) '開始查詢
If stumrc.RecordCount = 0 Then
MsgBox "查詢無記錄", 0 + 48, "提示"
Combo1(0).SetFocus
MSHFlexGrid1.Rows = 1
Else
With MSHFlexGrid1 '填入標題
.Rows = 1
.CellAlignment = 4
.ColAlignment = 2
.TextMatrix(0, 0) = "卡號"
.TextMatrix(0, 1) = "學號"
.TextMatrix(0, 2) = "姓名"
.TextMatrix(0, 3) = "性別"
.TextMatrix(0, 4) = "系別"
.TextMatrix(0, 5) = "年級"
.TextMatrix(0, 6) = "班級"
.TextMatrix(0, 7) = "金額"
.TextMatrix(0, 8) = "備註"
.TextMatrix(0, 9) = "狀態"
.TextMatrix(0, 10) = "日期"
.TextMatrix(0, 11) = "時間"
.TextMatrix(0, 12) = "型別"
Do While Not stumrc.EOF '顯示查詢資料
.Rows = .Rows + 1
.TextMatrix(.Rows - 1, 0) = stumrc.Fields(0)
.TextMatrix(.Rows - 1, 1) = stumrc.Fields(1)
.TextMatrix(.Rows - 1, 2) = stumrc.Fields(2)
.TextMatrix(.Rows - 1, 3) = stumrc.Fields(3)
.TextMatrix(.Rows - 1, 4) = stumrc.Fields(4)
.TextMatrix(.Rows - 1, 5) = stumrc.Fields(5)
.TextMatrix(.Rows - 1, 6) = stumrc.Fields(6)
.TextMatrix(.Rows - 1, 7) = stumrc.Fields(7)
.TextMatrix(.Rows - 1, 8) = stumrc.Fields(8)
.TextMatrix(.Rows - 1, 9) = stumrc.Fields(10)
.TextMatrix(.Rows - 1, 10) = stumrc.Fields(12)
.TextMatrix(.Rows - 1, 11) = stumrc.Fields(13)
.TextMatrix(.Rows - 1, 12) = stumrc.Fields(14)
stumrc.MoveNext
Loop
End With
End If
stumrc.Close
總結：搞清邏輯之後，其實實現起來並不難，感謝大家閱讀，如有錯誤，還請大家指正