如何使用vb 2010从访问数据库中获取和显示数据

Am just new to vb 2010 and am trying to fetch data from access database (Employees.mdb) but am stack on how to display the data now, anybody with help. Thanks

我刚接触vb 2010,我正在尝试从访问数据库(Employees.mdb)中获取数据,但现在是如何显示数据的堆栈,任何有帮助的人。谢谢

Public Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    Dim LoginUser As String
    LoginUser = LoginForm.TextBoxID.Text ' User Login Name
    DisplayLogin.Text = LoginUser ' Display now user to form

    Dim db As String = "Employees.mdb"

    Dim DatabasePath As String = System.Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) + "\QBook Api\data api\" + db
    If My.Computer.FileSystem.FileExists(DatabasePath) Then
        Dim con As New OleDb.OleDbConnection
        Dim cmd As New OleDb.OleDbCommand
        Dim Sql As String
        Dim NumOfRows As Integer
        Dim TodayDate As String = Today
        con.ConnectionString = "PROVIDER = Microsoft.Jet.OLEDB.4.0; Data Source = " + DatabasePath

        con.Open() ' Opening oLe Connection

        ' Checking database if we have todays or Searched records
        Sql = "SELECT * FROM Employees INNER JOIN TimeTable ON Employees.EmployeeNo = TimeTable.RefID WHERE Dated = '" & TodayDate & "' "
        cmd = New OleDb.OleDbCommand(Sql, con)
        NumOfRows = cmd.ExecuteScalar()
        cmd.ExecuteNonQuery()
        If NumOfRows > 0 Then
            ' Here I need to display the data


        Else
            MsgBox("Sorry we don’t have Entry Logs of (" + TodayDate + ")", MsgBoxStyle.Critical, Title:="QBook - No entry found")
        End If
        con.Close() ' Closing Connection
    Else

        MsgBox("Unable to get database file in (" + DatabasePath + ")", MsgBoxStyle.Critical)

    End If ' no database found




End Sub

any suggestion is appreciated and welcomed

任何建议都表示赞赏和欢迎

1 个解决方案

#1

ExecuteScalar only returns the first column from the first row in your result set so you won't be able to display any data other than that. It's typically used if you're getting a count, sum or something that only returns one value.

ExecuteScalar仅返回结果集中第一行的第一列,因此您将无法显示除此之外的任何数据。如果您获得计数,总和或只返回一个值的东西,通常会使用它。

If you want to read and display data use ExecuteReader (https://msdn.microsoft.com/en-us/library/979byfca(v=vs.110).aspx) instead. You can then use that to bind your result to something like a DataGridView.

如果要读取和显示数据,请使用ExecuteReader(https://msdn.microsoft.com/en-us/library/979byfca(v=vs.110).aspx)。然后,您可以使用它将结果绑定到类似DataGridView的内容。

Dim reader = cmd.ExecuteReader(CommandBehavior.CloseConnection)

If reader.HasRows() Then
    Dim dt = New DataTable()
    dt.Load(reader)
    dataGridView2.DataSource = dt
Else
    'No log entries to display
End If