title: Use of GROUP BY in SQL
body: <p>QUESTION: Which release_year had the most language diversity?</p>
  <p>HINT: Most language diversity&quot; can be interpreted as COUNT(DISTINCT ___).</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>id</th>
  <th>title</th>
  <th>release_year</th>
  <th>country</th>
  <th>duration</th>
  <th>language</th>
  <th>certification</th>
  <th>gross</th>
  <th>budget</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>1</td>
  <td>Intolerance: Love's Struggle Throughout the Ages</td>
  <td>1916</td>
  <td>USA</td>
  <td>123</td>
  <td>null</td>
  <td>not rated</td>
  <td>null</td>
  <td>385907</td>
  </tr>
  <tr>
  <td>2</td>
  <td>Over the Hill to the Poorhouse</td>
  <td>1915</td>
  <td>Germany</td>
  <td>523</td>
  <td>german</td>
  <td>rated</td>
  <td>null</td>
  <td>385907</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>These are the fields given. How can I get the release_year in which there is the maximum language diversity?</p>
  <pre><code>SELECT COUNT(DISTINCT release_year)
  FROM films
  GROUP BY release_year
  </code></pre>