title: How to handle the stock table quantity after sale
body: <p>I have a problem. I am not understanding that how to deduct the quantity from stock after sale and we have multiple entries of same stock
  like:</p>
  <br>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th style="text-align: left;">id</th>
  <th style="text-align: left;">Medicine</th>
  <th style="text-align: left;">Company</th>
  <th style="text-align: left;">quantity</th>
  <th style="text-align: left;">item price</th>
  <th style="text-align: left;">is deleted</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td style="text-align: left;">1</td>
  <td style="text-align: left;">Panadol</td>
  <td style="text-align: left;">Abbott</td>
  <td style="text-align: left;">200</td>
  <td style="text-align: left;">10.00</td>
  <td style="text-align: left;">0</td>
  </tr>
  <tr>
  <td style="text-align: left;">2</td>
  <td style="text-align: left;">Panadol</td>
  <td style="text-align: left;">Abbott</td>
  <td style="text-align: left;">100</td>
  <td style="text-align: left;">11.00</td>
  <td style="text-align: left;">0</td>
  </tr>
  <tr>
  <td style="text-align: left;">3</td>
  <td style="text-align: left;">Panadol</td>
  <td style="text-align: left;">Abbott</td>
  <td style="text-align: left;">100</td>
  <td style="text-align: left;">12.00</td>
  <td style="text-align: left;">0</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>now how to deduct the quantity of stock and  one thing is more that this product/Medicine has separate manufacturing and expiry date
  please tell me how to handle it.
  I was thinking that to make separate table for tracking  the remaining stock quantity.
  or runtime management to calculate all the sale quantity minus(-) sum of all quantities entered to get
  the current stock quantity.
  Please guide me.</p>