ช่วยหน่อย sql กับฐานข้อมูล access ต้องเขียนยังไงถึงจะได้ข้อมูลครบ

rpt_ImPort.Detail = "SELECT  T_ImportHeader.ImportNo,ImportStatus,ImportDate,DocRef,ImportType," & _
 "ILineNo,T_ImportDetail.ProductCode,' ' as ProductName,T_ImportDetail.Logo,T_ImportDetail.ProductType,T_ImportDetail.Brand,T_ImportDetail.Qty " & _
   "  FROM  T_ImportHeader,T_ImportDetail " & _
   "   WHERE  (  T_ImportHeader.ImportNo  LIKE  @ImportNo AND   ImportStatus  LIKE  @ImportStatus  AND  DocRef  LIKE  @DocRef  AND  ImportType  LIKE  @ImportType   AND T_ImportHeader.ImportNo=T_ImportDetail.ImportNo   " & _
  "  AND  ImportDate  BETWEEN   @ImportDateFrom    AND   @ImportDateTo  )" & _
  "  ORDER  BY  T_ImportHeader.ImportNo,ILineNo  ASC  "

  Private Function LoadDataHead() As DataTable

        Dim com As New OleDbCommand
        Dim dr As OleDbDataReader
        Dim dt As DataTable



        Dim _ImportNo As String = "%" & tbImportNo.Text.Trim & "%"
        Dim _DocRef As String = "%" & tbDocRef.Text.Trim & "%"
        Dim _status As String = "%" & cbStatus.SelectedItem & "%"
        Dim _ImportDateFrom As Date = dtImportDateForm.Value
        Dim _ImportDateTo As Date = dtImportDateTo.Value
        Dim _IMType As String = "%" & cbIMType.SelectedItem & "%"

    
        With com
            .CommandText = rpt_ImPort.Detail
            .CommandType = CommandType.Text
            .Connection = Conn
            .Transaction = tr
            .Parameters.Clear()
            .Parameters.Add("@ImportNo", OleDbType.VarChar).Value = _ImportNo
            .Parameters.Add("@ImportStatus", OleDbType.VarChar).Value = _status
            .Parameters.Add("@DocRef", OleDbType.VarChar).Value = _DocRef
            .Parameters.Add("@ImportType", OleDbType.VarChar).Value = _IMType
            .Parameters.Add("@ImportDateFrom", OleDbType.Date).Value = _ImportDateFrom
            .Parameters.Add("@ImportDateTo", OleDbType.Date).Value = _ImportDateTo


            dr = .ExecuteReader()

            dt = New DataTable
            dt.Load(dr)

            If dt.Rows.Count > 0 Then   ' err ว่าอ่านค่าได้อย่างเดียว ทำยังไงถึงจะเก็บค่าได้
                Dim drow As DataRow
                Dim i As Integer = 0
                For Each drow In dt.Rows
                    drow("ProductName") = Me.GetCustomerName(drow("ProductCode"))
                Next
            End If
        End With


        Return dt
    End Function

    Private Function GetCustomerName(ByVal customerName As String) As String
        Dim bs As New DataViewManager
        Dim datagv As New DataGridView
        Dim ds2 As New DataSet()
        Dim sqlCompany As String = ""
        sqlCompany = "SELECT * FROM M_Customer   "
        sqlCompany = sqlCompany & " WHERE   (CustomerCode='" & customerName & "')"
        da = New OleDbDataAdapter(sqlCompany, Conn)
        ds2.Tables.Clear()
        da.Fill(ds2, "Customer")
        datagv.DataSource = ds2.Tables("Customer")

        If ds2.Tables("Customer").Rows.Count > 0 Then
            customerName = ds2.Tables("Customer").Rows(0).Item("CustomerNameTH")
        End If
        Return customerName
    End Function