title: SQL - avoid repeated column values
body: <pre><code>SELECT t.id, apa.district AS district
  FROM tbl_activity AS t
  JOIN tbl_activity_package AS ap ON ap.activity_id = t.id
  JOIN tbl_activity_package_address AS apa ON apa.activity_package_id = ap.id
  GROUP BY t.id
  ORDER BY apa.district
  </code></pre>
  
  <p>After querying, the output is:</p>
  
  <p><img src="https://i.stack.imgur.com/tmV65.png" alt="output"></p>
  
  <p>I want to return only one row by district. How can I do that in the query?</p>