ขอคำแนะนำ select data ส่วนลดของสินค้าหน่อยครับ vb.net(win app)

Dim dtfInfo As DateTimeFormatInfo
 sqlStr = " Select p.ProductID ,p.ProductName,p.ProductSale,pd.Discount,Sum (s.StockBalance) as Balance "
            sqlStr += " FROM Product p left join PromotionDetail pd on p.ProductID = pd.ProductID left join Stock s on p.ProductID = s.ProductID "
            sqlStr += "left join Promotion pr on pr.PromotionID = pd.PromotionID"
            sqlStr += " Where p.ProductID = '" & Str & "' "
            sqlStr += " AND s.Status = 'I'"
            sqlStr += " Group By p.ProductID,p.ProductName,p.ProductSale,pd.Discount"

            da = New SqlDataAdapter(sqlStr, Conn)
            da.Fill(ds, "Product")
            dtTable11 = ds.Tables("Product")

            TotalRecord = dtTable11.Rows.Count
            If TotalRecord = 1 Then
                ClearBinding()
                txtSearch.DataBindings.Add("Text", ds.Tables("Product"), "ProductID")
                lblproductname.DataBindings.Add("Text", ds.Tables("Product"), "ProductName")
                txtLastCost.DataBindings.Add("Text", ds.Tables("Product"), "ProductSale")
                txtStockQty.DataBindings.Add("Text", ds.Tables("Product"), "Balance")
                txtAmount.Focus()
                txtAmount.SelectAll()
                'dr.Close()
            End If

            sqlStr = " Select p.ProductID,pd.Discount,StartDate,EndDate "
            sqlStr += " FROM Product p left join PromotionDetail pd on p.ProductID = pd.ProductID left join Stock s on p.ProductID = s.ProductID "
            sqlStr += "left join Promotion pr on pr.PromotionID = pd.PromotionID"
            sqlStr += " Where '" & DtpSell.Value.ToString("s", dtfInfo) & "' BETWEEN StartDate And EndDate"

            da = New SqlDataAdapter(sqlStr, Conn)
            da.Fill(ds, "Promotion")
            dtTable12 = ds.Tables("Promotion")

            TotalRecord = dtTable12.Rows.Count
            If TotalRecord = 1 Then
                txtDc.DataBindings.Add("Text", ds.Tables("Promotion"), "Discount")
            End If