title: rolling sum for each product each date
body: <p>If I have a table</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>Product</th>
  <th>date</th>
  <th>sold</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>A</td>
  <td>2022-01-01</td>
  <td>2</td>
  </tr>
  <tr>
  <td>A</td>
  <td>2022-01-04</td>
  <td>3</td>
  </tr>
  <tr>
  <td>A</td>
  <td>2022-01-06</td>
  <td>1</td>
  </tr>
  <tr>
  <td>B</td>
  <td>2022-01-05</td>
  <td>4</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>How can I find out the rolling sum of sold for past 4 days for each product in bigquery sql?
  result looking for:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>Product</th>
  <th>date</th>
  <th>rolling sum</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>A</td>
  <td>2022-01-01</td>
  <td>2</td>
  </tr>
  <tr>
  <td>A</td>
  <td>2022-01-02</td>
  <td>2</td>
  </tr>
  <tr>
  <td>A</td>
  <td>2022-01-03</td>
  <td>2</td>
  </tr>
  <tr>
  <td>A</td>
  <td>2022-01-04</td>
  <td>5</td>
  </tr>
  <tr>
  <td>A</td>
  <td>2022-01-05</td>
  <td>3</td>
  </tr>
  <tr>
  <td>A</td>
  <td>2022-01-06</td>
  <td>4</td>
  </tr>
  <tr>
  <td>B</td>
  <td>2022-01-01</td>
  <td>0</td>
  </tr>
  <tr>
  <td>B</td>
  <td>2022-01-02</td>
  <td>0</td>
  </tr>
  <tr>
  <td>B</td>
  <td>2022-01-03</td>
  <td>0</td>
  </tr>
  <tr>
  <td>B</td>
  <td>2022-01-04</td>
  <td>0</td>
  </tr>
  <tr>
  <td>B</td>
  <td>2022-01-05</td>
  <td>4</td>
  </tr>
  <tr>
  <td>B</td>
  <td>2022-01-06</td>
  <td>4</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>The major issue is there is no record if there is no product sold.</p>