vb dataset

小弟刚学···问题有时候会雷人····望大侠~~
Dim conn As OleDbConnection = New OleDbConnection
        Dim cmd As OleDbCommand = New OleDbCommand
        Dim da As OleDbDataAdapter = New OleDbDataAdapter
        Dim ds As DataSet = New DataSet
        conn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\vb\vbnetDB\dbtest.mdb"
        conn.Open()
        cmd.Connection = conn
         = "select * from student，tuser"
        da.SelectCommand = cmd
        da.Fill(ds, "student")
        Me.DataGrid1.DataSource = ds.Tables("student")
        conn.Close()