title: SQL need groups
body: <p>I want to group unique rows from 1 table that may have many rows in table 2.</p>
  
  <p>If I do make this query:</p>
  
  <pre><code>SELECT c.`lastname`,a.`city`
  FROM `customer` c
  LEFT JOIN `visit` a ON (c.`id` = a.`id`);
  </code></pre>
  
  <p>I get results like this:</p>
  
  <pre><code>lastname |city
  -------- |----
  DOE      |Paris 
  DOE      |Miami
  Technical|Toronto
  Technical|d
  M        |toronto
  mavya    |TORONTO
  lname    |NULL
  </code></pre>
  
  <p>(Both <code>customer</code> and <code>visit</code> tables also have <code>id</code>s that I'm joining, but not showing here).</p>
  
  <p><strong>How can I get results like below?</strong> (Can I get SQL to return an array inside results?)</p>
  
  <pre><code>lastname |city
  -------- |----
  DOE      |Paris,Miami
  Technical|Toronto,d
  M        |toronto
  mavya    |TORONTO
  lname    |NULL
  </code></pre>