Child table with 100% width extends parent

Question

at the moment I am trying to create a child table, that can have a width of more than 100% of the parent. Therefor they should have a scrollbar. But, when I try this with my

Answer 1

You need to use table-layout:fixed; ^ref. the automatic layout may give unexpected result.

Fixed table layout

With this (fast) algorithm, the horizontal layout of the table does not depend on the contents of the cells; it only depends on the table's width, the width of the columns, and borders or cell spacing.

As a side note, the same issue happen with or without width:100%

body {
  margin: 0;
  padding: 0;
  width: 100%;
  background-color: green;
}

.main {
  margin: 0 10%;
  padding: 00;
  width: 80%;
  display: table;
}

table {
  margin: 0;
  padding: 0;
  display: block;
  overflow-x: auto;
  white-space: nowrap;
}

<main class="main">
  <table>
    <tr>
      <td>A very very very veeeeeeeeeeeeeeeeeeeeery loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong line</td>
      <td>...</td>
    </tr>
    <tr>
      <td>...</td>
      <td>...</td>
    </tr>
    <tr>
      <td>...</td>
      <td>...</td>
    </tr>
  </table>
</main>
<main class="main" style="table-layout: fixed;">
  <table>
    <tr>
      <td>A very very very veeeeeeeeeeeeeeeeeeeeery loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong line</td>
      <td>...</td>
    </tr>
    <tr>
      <td>...</td>
      <td>...</td>
    </tr>
    <tr>
      <td>...</td>
      <td>...</td>
    </tr>
  </table>
</main>