title: Use a comma-separated string in an `IN ()` in MySQL
body: <p>If a user-defined variable <code>@x</code> is a string of comma separated numbers, e.g. <code>'1,2,4'</code>, is there a way to use it in an <code>IN ()</code> function?</p>
  
  <p>Specifically:</p>
  
  <pre><code>SET @x := '1,2,4';
  SELECT * FROM t WHERE c IN (@x);
  </code></pre>
  
  <p>does not select rows in t where c equals 1 or 2 or 4.</p>