Mysql เปรียบเทียบค่า2ตาราง มาก-น้อยต่างกัน ใช้ where ยังไงครับ

 Private Sub Bind_dgv_small()

        conn.Open()
        Dim strSQL As String = "select (product.id_code) as id,(product.code) as code,(product.name_) as name_,(product_cat.cat_name) as cat_name,(product.sell) as sell " + _
                       ",CONCAT(sum(product_in_out.num - product_in_out.num_sell)),' ',product_pack.pack_name as sum_stock ,if(product.status = '1','สมบูรณ์','ระงับ') as status " + _
                      "from product,product_in_out,product_cat,product_pack where (product.id_code = product_in_out.id_code) and (product.id_cat = product_cat.id) and (product.id_pack = product_pack.id) and (product_in_out.status = '1') and (product.low >= sum_stock) group by product_in_out.id_code  order by product.name_"



        strSQL_print = strSQL

        Dim Cmd As New MySqlCommand(strSQL, conn)
        Dim adaptre As New MySqlDataAdapter(Cmd)
        Dim data As New DataSet()
        adaptre.Fill(data, "data_all")
        lbl_reccord.Text = data.Tables("data_all").Rows.Count()
        dgv.DataSource = data.Tables("data_all")
        dgv.Columns.Clear()

        Dim column As DataGridViewTextBoxColumn

        column = New DataGridViewTextBoxColumn()
        column.DataPropertyName = "id"
        column.HeaderText = ""
        column.Width = 0
        dgv.Columns.Add(column)
        dgv.Columns(0).Visible = False 'ซ่อน column

        column = New DataGridViewTextBoxColumn()
        column.DataPropertyName = "code"
        column.HeaderText = "รหัส"
        column.Width = 130
        dgv.Columns.Add(column)

        column = New DataGridViewTextBoxColumn()
        column.DataPropertyName = "name_"
        column.HeaderText = "ชื่อสินค้า"
        column.Width = 150
        dgv.Columns.Add(column)


        column = New DataGridViewTextBoxColumn()
        column.DataPropertyName = "cat_name"
        column.HeaderText = "ประเภทสินค้า"
        column.Width = 120
        dgv.Columns.Add(column)



        column = New DataGridViewTextBoxColumn()
        column.DataPropertyName = "sell"
        column.HeaderText = "ราคาขาย"
        column.Width = 90
        dgv.Columns.Add(column)

        column = New DataGridViewTextBoxColumn()
        column.DataPropertyName = "sum_stock"
        column.HeaderText = "จำนวนสต๊อก"
        column.Width = 110
        dgv.Columns.Add(column)

        column = New DataGridViewTextBoxColumn()
        column.DataPropertyName = "status"
        column.HeaderText = "สถานะ"
        column.Width = 80
        dgv.Columns.Add(column)



        conn.Close()



        If lbl_reccord.Text = "0" Then
            btn_print.Enabled = False
        Else
            btn_print.Enabled = True
        End If
    End Sub