我创建了一个添加和返回设备的程序，我的问题是，因为我的借阅表和我的返回设备表只在一个表中..代表这些字段
“productnumber”
“产品名”
“dateborrowed”
“datereturned”
“borrowername”
“状态”
我想在这里做的是当用户返回设备时，在字段上输入相同的数据会在我的数据库上出错...特别是在我的产品编号上，因为那是我的主键，所以我决定有一个数据我的返回设备表单中的网格，所以如果用户返回一个设备，我所要做的就是更新我的数据库中的datereurned字段。你可以帮我解释一下代码吗？
答案 0 :(得分：2)
由于您没有明确指出您需要帮助的内容，我将首先向您提供执行更新的简单查询，然后我将向您展示如何与Access进行交互。
更新datereturned的查询：
str = "UPDATE 'Your Table Name' SET datereturned = " & now ' This is your update query.
要做的第一件事是创建Access数据库的连接：
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 )
发现于：
http://p2p.wrox.com/ado-net/28703-how-vbulletin-net-connect-access-database.html
接下来，您应该执行更新：
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
这是一个允许您轻松简单地执行交互的课程。
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
发现于：
答案 1 :(得分：1)
您需要拆分产品并将数据借入/返回两个表：
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)
借款人/客户的第三张表也将按顺序排列
borrowers:
borrowerID
"borrowername"