更新域通的Visual Basic

Question

我創建了一個程序，添加和返回設備，我的問題是，它是因爲我借用表，我回設備表是在一個表only..representing這些領域

「productnumber」

「產品名稱」

「dateborrowed」

「datereturned」

「博rrowername」

‘狀態’

當用戶返回設備，進入上字段相同的數據將使我productnumber我database..especially錯誤，因爲這是我想在這裏做什麼是我的主鍵，所以我決定在我的返回設備表單中有一個數據網格，所以如果用戶返回一個設備，我所要做的就是更新我的數據庫中的datereturned字段。你能幫我解碼嗎？

Answer 1

由於您沒有具體說明您需要什麼幫助，我將首先給您簡單的查詢來執行更新，然後我將向您展示如何與Access進行交互。

查詢更新datereturned：

str = "UPDATE 'Your Table Name' SET datereturned = " & now ' This is your update query. 

首先要做的就是創建一個連接Access數據庫：

 Dim connectionString As String = "Provider=Microsoft.Jet.OLEDB.4.0; Ole DB Services=-4; Data Source=D:\Tecnical Stu"& _ 
"dy\Complete_Code\Ch08\data\NorthWind.mdb" 
     Dim dbConnection As System.Data.IDbConnection = New System.Data.OleDb.OleDbConnection(connectionString) 

找到在：

http://p2p.wrox.com/ado-net/28703-how-vbulletin-net-connect-access-database.html

下一頁你應該執行更新：

dbConnection .Open() 
str = "UPDATE 'Your Table Name' SET datereturned = " & now ' This is your update query. 
'string stores the command and CInt is used to convert number to string 
cmd = New OleDbCommand(str, cn) 
icount = cmd.ExecuteNonQuery 

這裏有一個類可以讓你輕鬆簡單地進行交互。

Imports System.Data.OleDb 
Public Class Form1 Inherits System.Windows.Forms.Form 
Dim cn As OleDbConnection 
Dim cmd As OleDbCommand 
Dim dr As OleDbDataReader 
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e as _ 
System.EventArgs) Handles MyBase.Load 
End Sub 

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As_ 
System.EventArgs) Handles Button1.Click 
Try 
cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;_ 
Data Source=C:\emp.mdb;") 
'provider to be used when working with access database 
cn.Open() 
cmd = New OleDbCommand("select * from table1", cn) 
dr = cmd.ExecuteReader 
While dr.Read() 
TextBox1.Text = dr(0) 
TextBox2.Text = dr(1) 
TextBox3.Text = dr(2) 
' loading data into TextBoxes by column index 
End While 
Catch 
End Try 
dr.Close() 
cn.Close() 
End Sub 
End Class 
When you run the code and click the Button, records from Table1 of the Emp database will be displayed in the TextBoxes. 

Retrieving records with a Console Application 

Imports System.Data.OleDb 
Imports System.Console 
Module Module1 

Dim cn As OleDbConnection 
Dim cmd As OleDbCommand 
Dim dr As OleDbDataReader 

Sub Main() 
Try 
cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\emp.mdb;_ 
Persist Security Info=False") 
cn.Open() 
cmd = New OleDbCommand("select * from table1", cn) 
dr = cmd.ExecuteReader 
While dr.Read() 
WriteLine(dr(0)) 
WriteLine(dr(1)) 
WriteLine(dr(2)) 
'writing to console 
End While 
Catch 
End Try 
dr.Close() 
cn.Close() 
End Sub 

End Module 
Code for Inserting a Record 

Imports System.Data.OleDb 
Public Class Form2 Inherits System.Windows.Forms.Form 
Dim cn As OleDbConnection 
Dim cmd As OleDbCommand 
Dim dr As OleDbDataReader 
Dim icount As Integer 
Dim str As String 

Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As_ 
System.EventArgs) Handles MyBase.Load 

End Sub 

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As_ 
System.EventArgs) Handles Button2.Click 
Try 
cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\emp.mdb;") 
cn.Open() 
str = "insert into table1 values(" & CInt(TextBox1.Text) & ",'" & TextBox2.Text & "','" &_ 
TextBox3.Text & "')" 
'string stores the command and CInt is used to convert number to string 
cmd = New OleDbCommand(str, cn) 
icount = cmd.ExecuteNonQuery 
MessageBox.Show(icount) 
'displays number of records inserted 
Catch 
End Try 
cn.Close() 
End Sub 
End Class 

找到在：

http://www.startvbdotnet.com/ado/msaccess.aspx

Answer 2

你需要返回數據拆分的產品和借/成兩個表：

product: 
"productnumber" 
"productname" 

borrowed: 
borrowedID (use a simple autonumber) 
productnumber (foreign key linked to productnumber in the product table) 
"dateborrowed" 
"datereturned" 
"status" 
borrowerID (foreign key linked to borrower table) 

第三個表對借款人/客戶也將按順序排列

borrowers: 
borrowerID 
"borrowername"