如何用CSS实现嵌套表与父表宽度匹配

<div class="parent-table">
  <table>
    <tr>
      <td>父表格</td>
      <td>
        <div class="nested-table">
          <table>
            <tr>
              <td>子表格</td>
              <td>子表格</td>
            </tr>
          </table>
        </div>
      </td>
    </tr>
  </table>
</div>

.parent-table {
  position: relative;
  width: 100%;
}

.nested-table {
  position: absolute;
  left: 0;
  right: 0;
}

.nested-table table {
  width: 100%;
}

.parent-table table,
.nested-table table {
  border-collapse: collapse;
}

.parent-table td,
.nested-table td {
  border: 1px solid black;
  padding: 5px;
}