Html – How to fix a dropdown menu appearing behind a sticky column in table

/* Dropdown Button */
.dropbtn {
  background-color: #04aa6d;
  color: white;
  padding: 16px;
  font-size: 16px;
  border: none;
  z-index: 99999;
}

/* The container <div> - needed to position the dropdown content */
.dropdown {
  position: relative;
  display: inline-block;
}

/* Dropdown Content (Hidden by Default) */
.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f1f1f1;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 99999;
}

/* Links inside the dropdown */
.dropdown-content a {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
}

/* Change color of dropdown links on hover */
.dropdown-content a:hover {
  background-color: #ddd;
}

/* Show the dropdown menu on hover */
.dropdown:hover .dropdown-content {
  display: block;
}

/* Change the background color of the dropdown button when the dropdown content is shown */
.dropdown:hover .dropbtn {
  background-color: #3e8e41;
  z-index: 9999;
}

.container {
  max-width: 500px;
  margin: auto;
  margin-top: 3rem;
  overflow-x: auto;
}

table {
  font-family: "Open Sans", sans-serif;
  position: relative;
  border-collapse: collapse;
  border-spacing: 0;
  table-layout: auto;
  width: 100%;
  border: none;
  border-radius: 0.5rem;
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  white-space: nowrap;
}
table * {
  border: none;
}
table thead tr {
  color: #2d3748;
  font-size: 1rem;
  font-weight: 500;
  text-align: left;
}
table thead tr th {
  background: #edf2f7;
  padding: 0.75rem 1.5rem;
  vertical-align: middle;
}
table tbody tr:nth-child(odd) td {
  background: #ffffff;
}
table tbody tr:nth-child(even) td {
  background: #edf2f7;
}
table tbody td {
  color: #1a202c;
  text-align: left;
  padding: 1.5rem 1.5rem;
  vertical-align: middle;
  font-size: 1.125rem;
  font-weight: normal;
}
table tr:last-child td:first-child {
  border-bottom-left-radius: 0.5rem;
}
table th:first-child {
  border-top-left-radius: 0.5rem;
}
table tr:last-child td:last-child {
  border-bottom-right-radius: 0.5rem;
}
table th:last-child {
  border-top-right-radius: 0.5rem;
}
table tr > th:first-child,
table tr > td:first-child {
  position: sticky;
  z-index: 2;
  left: 0;
}

tr {
  position: relative;
}

tr:nth-of-type(1) {
  z-index: 10;
}

tr:nth-of-type(2) {
  z-index: 9;
}

tr:nth-of-type(3) {
  z-index: 8;
}

tr:nth-of-type(4) {
  z-index: 7;
}

<div class="container">
  <table>
    <thead>
      <tr>
        <th>DATA1</th>
        <th>DATA2</th>
        <th>DATA3</th>
        <th>DATA4</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td>
          <div class="dropdown">
            <button class="dropbtn">Dropdown</button>
            <div class="dropdown-content">
              <a href="#">Link 1</a>
              <a href="#">Link 2</a>
              <a href="#">Link 3</a>
            </div>
          </div>
        </td>
        <td>Some values</td>
        <td>Some values</td>
        <td>Some values</td>
      </tr>
      <tr>
        <td>
          <div class="dropdown">
            <button class="dropbtn">Dropdown</button>
            <div class="dropdown-content">
              <a href="#">Link 1</a>
              <a href="#">Link 2</a>
              <a href="#">Link 3</a>
            </div>
          </div>
        </td>
        <td>Other values</td>
        <td>Other values</td>
        <td>Other values</td>
      </tr>
      <tr>
        <td>
          <div class="dropdown">
            <button class="dropbtn">Dropdown</button>
            <div class="dropdown-content">
              <a href="#">Link 1</a>
              <a href="#">Link 2</a>
              <a href="#">Link 3</a>
            </div>
          </div>
        </td>
        <td>Other values</td>
        <td>Other values</td>
        <td>Other values</td>
      </tr>
      <tr>
        <td>
          <div class="dropdown">
            <button class="dropbtn">Dropdown</button>
            <div class="dropdown-content">
              <a href="#">Link 1</a>
              <a href="#">Link 2</a>
              <a href="#">Link 3</a>
            </div>
          </div>
        </td>
        <td>Other values</td>
        <td>Other values</td>
        <td>Other values</td>
      </tr>
    </tbody>
  </table>
</div>