รบกวนพี่ๆครับ ต้องการน้ำ คอลัม1+คอลั่ม2 แล้วเก็บผลลัพธ์ไว้ที่ คอลั่ม3

 Private Sub ShowData()
        Dim sql As String = ""
        sb.Remove(0, sb.Length())
        sb.Append("SELECT RentDetail.RentID, RentDetail.FameID, Fame.FameName, Fame.Category, Customer.CusName, Rent.RentDate, Rent.ReturnDate, Rent.RentStatus ")
        sb.Append(" FROM RentDetail,Fame,Rent,Customer")
        sb.Append(" WHERE RentDetail.FameID=Fame.FameID")
        sb.Append(" AND RentDetail.RentID=Rent.RentID")
        sb.Append(" AND Rent.CusID=Customer.CusID")
        'sb.Append("SELECT RentDetail.RentID, RentDetail.FameID, Fame.FameName, Fame.Category, Rent.RentDate FROM RentDetail INNER JOIN Fame ON (RentDetail.FameID=Fame.FameID) INNER JOIN Rent ON (Rent.RentID = RentDetail.RentID)")
        'sb.Append(" INNER JOIN Rent ON RentDetail.RentID=Rent.RentID")
        sql = sb.ToString


        If IsFind = True Then
            ds.Tables("RentDetail").Clear()
        End If
        da = New OleDbDataAdapter(sql, Conn)
        da.Fill(ds, "RentDetail")
        If ds.Tables("RentDetail").Rows.Count <> 0 Then


            IsFind = True

                With dgvFile
                    .ReadOnly = True
                .DataSource = ds.Tables("RentDetail")

           


                End With
        Else
                IsFind = True
                dgvFile.DataSource = Nothing
                MessageBox.Show("ไม่พบรายการในฐานข้อมูล", "ผลการทำงาน", MessageBoxButtons.OK, MessageBoxIcon.Information)
        End If




        FormatDatagrid()
    End Sub