機房收費系統——組合查詢 1.0
阿新 • • 發佈：2018-12-30
一、引言
組合查詢這個問題是我機房收費系統遇到的第一個難題！而且困擾了我很久！
主要有兩個問題：
第一是邏輯上的問題！
第二是資料庫查詢上的問題！
接下來就說說這兩個問題。
二、組合邏輯
一共有三組查詢條件，兩個組合！
難點：使用者選擇選擇條件及其組合情況的判斷
最簡單的解決辦法就算是按照正常的邏輯，一條一條的進行判斷！
簡單的畫了一個流程圖！
這個流程非常容易理解！程式碼也很容易實現！
三、組合查詢語句
1、只有一個條件的時候的查詢
txtSQL = "select * from student_info where " & field(Trim(ziduancombo1.Text 注：field為用來轉換combo中的選項，將他們與資料庫中的列名對應起來！
field用之前需要定義！
Public Function field(i As String) As String
Select Case ziduancombo1.Text
Case "卡號"
field = "cardno"
Case "學號"
field = "studentno"
Case "姓名"
field = "studentname" 2、兩個條件進行組合查詢語句
txtSQL = txtSQL & strzuhecombo1 & " " & field(Trim(ziduancombo2.Text 注：strzuhecombo1需要定義，用來轉換“或”和“與”，使之能夠被資料庫識別
Select Case zuhecombo1.Text
Case "與"
strzuhecombo1 = "and"
Case "或"
strzuhecombo1 = "or"
End Select3、三個條件進行組合查詢語句
txtSQL = txtSQL & strzuhecombo2 & " " & field(Trim(ziduancombo3.Text)) & Trim(caozuofucombo3.Text) & "'" & Trim(txtchaxun3.Text) & "'"四、整個過程程式碼
Private Sub cmdok_Click()
If Trim(ziduancombo1.Text) = "" Then
MsgBox "請選擇欄位！", vbOKOnly + vbExclamation, "警告"
ziduancombo1.SetFocus
Else
If Trim(caozuofucombo1.Text) = "" Then
MsgBox "請選擇操作符！", vbOKOnly + vbExclamation, "警告"
caozuofucombo1.SetFocus
Else
If Trim(txtchaxun1.Text) = "" Then
MsgBox "請輸入要查詢的內容！", vbOKOnly + vbExclamation, "警告"
txtchaxun1.SetFocus
Exit Sub
Else
'執行查詢
txtSQL = "select * from student_info where " & field(Trim(ziduancombo1.Text)) & Trim(caozuofucombo1.Text) & "'" & Trim(txtchaxun1.Text) & "'"
'判斷第一個組合條件時為空
If Trim(zuhecombo1.Text) = "" Then '此時沒有組合查詢
Set mrc = executeSQL(txtSQL, msgtext)
If mrc.EOF = True Then
MsgBox "沒有該記錄！", vbOKOnly + vbExclamation, "提示"
Exit Sub
End If
Else
'選擇了組合條件1時進行組合查詢
If Trim(ziduancombo2.Text) = "" Then
MsgBox "請將查詢條件填寫完整！", vbOKOnly + vbExclamation, "提示"
ziduancombo2.SetFocus
Else
If Trim(caozuofucombo2.Text) = "" Then
MsgBox "請將查詢條件填寫完整！", vbOKOnly + vbExclamation, "提示"
caozuofucombo2.SetFocus
Else
If Trim(txtchaxun2.Text) = "" Then
MsgBox "請將查詢條件填寫完整！", vbOKOnly + vbExclamation, "提示"
txtchaxun2.SetFocus
Exit Sub
Else
If Trim(zuhecombo2.Text) = "" Then '第二個組合條件為空，進行前兩個的組合查詢
'執行查詢
Dim strzuhecombo1, strzuhecombo2 '定義變數用來轉換與和或
If zuhecombo1.Text <> "" Then
Select Case zuhecombo1.Text
Case "與"
strzuhecombo1 = "and"
Case "或"
strzuhecombo1 = "or"
End Select
End If
txtSQL = txtSQL & strzuhecombo1 & " " & field(Trim(ziduancombo2.Text)) & Trim(caozuofucombo2.Text) & "'" & Trim(txtchaxun2.Text) & "'"
Set mrc = executeSQL(txtSQL, msgtext)
If mrc.EOF = True Then
MsgBox "沒有此條記錄！", vbOKOnly + vbExclamation, "提示"
ziduancombo1.Text = ""
ziduancombo2.Text = ""
caozuofucombo1.Text = ""
caozuofucombo2.Text = ""
txtchaxun1.Text = ""
txtchaxun2.Text = ""
zuhecombo1.Text = ""
Exit Sub
End If
Else '如果第二個組合條件不為空時，對第三行的條件進行檢查
If Trim(ziduancombo3.Text) = "" Then
MsgBox "請將查詢條件填寫完整！", vbOKOnly + vbExclamation, "提示"
ziduancombo3.SetFocus
Else
If Trim(caozuofucombo3.Text) = "" Then
MsgBox "請將查詢條件填寫完整", vbOKOnly + vbExclamation, "提示"
caozuofucombo3.SetFocus
Else
If Trim(txtchaxun3.Text) = "" Then
MsgBox "請將查詢條件填寫完整！", vbOKOnly + vbExclamation, "提示"
txtchaxun3.SetFocus
Exit Sub
Else '都滿足條件後，進行組合查詢！
Select Case zuhecombo2.Text
Case "與"
strzuhecombo2 = "and"
Case "或"
strzuhecombo2 = "or"
End Select
txtSQL = txtSQL & strzuhecombo2 & " " & field(Trim(ziduancombo3.Text)) & Trim(caozuofucombo3.Text) & "'" & Trim(txtchaxun3.Text) & "'"
Set mrc = executeSQL(txtSQL, msgtext)
If mrc.EOF = True Then
MsgBox "沒有此條查詢記錄！", vbOKOnly + vbExclamation, "提示"
ziduancombo1.Text = ""
ziduancombo2.Text = ""
ziduancombo3.Text = ""
caozuofucombo1.Text = ""
caozuofucombo2.Text = ""
caozuofucombo3.Text = ""
txtchaxun1.Text = ""
txtchaxun2.Text = ""
txtchaxun3.Text = ""
zuhecombo1.Text = ""
zuhecombo2.Text = ""
End If
End If
End If
End If
End If
End If
End If
End If
End If
End If
End If
End If
'顯示查詢結果
With MSFgxinxichaxun
.Rows = 1
.CellAlignment = 4
.TextMatrix(0, 0) = "學號"
.TextMatrix(0, 1) = "姓名"
.TextMatrix(0, 2) = "卡號"
.TextMatrix(0, 3) = "金額"
.TextMatrix(0, 4) = "系別"
.TextMatrix(0, 5) = "年級"
.TextMatrix(0, 6) = "班級"
.TextMatrix(0, 7) = "性別"
.TextMatrix(0, 8) = "狀態"
.TextMatrix(0, 9) = "備註"
.TextMatrix(0, 10) = "型別"
.TextMatrix(0, 11) = "日期"
.TextMatrix(0, 12) = "時間"
Do While Not mrc.EOF
.Rows = .Rows + 1
.CellAlignment = 4
.TextMatrix(.Rows - 1, 0) = Trim(mrc.Fields(1))
.TextMatrix(.Rows - 1, 1) = Trim(mrc.Fields(2))
.TextMatrix(.Rows - 1, 2) = Trim(mrc.Fields(0))
.TextMatrix(.Rows - 1, 3) = Trim(mrc.Fields(7))
.TextMatrix(.Rows - 1, 4) = Trim(mrc.Fields(4))
.TextMatrix(.Rows - 1, 5) = Trim(mrc.Fields(5))
.TextMatrix(.Rows - 1, 6) = Trim(mrc.Fields(6))
.TextMatrix(.Rows - 1, 7) = Trim(mrc.Fields(3))
.TextMatrix(.Rows - 1, 8) = Trim(mrc.Fields(10))
.TextMatrix(.Rows - 1, 9) = Trim(mrc.Fields(8))
.TextMatrix(.Rows - 1, 10) = Trim(mrc.Fields(14))
.TextMatrix(.Rows - 1, 11) = Trim(mrc.Fields(12))
.TextMatrix(.Rows - 1, 12) = Trim(mrc.Fields(13))
'移動到下一條記錄
mrc.MoveNext
Loop
End With
End Sub一篇文章寫下來，覺得組合查詢並沒有那麼難！凡事都需要一個過程！學過了就要學會沉澱，這樣才能走的更遠！