title: How can I use an alias for a CONCAT in MySQL?
body: <p>I need to return an alias column <code>eventTitle</code> of which the content can be variable depending on whether another column's value is <code>null</code>. I also need to use the value of that alias to concatenate some other values to return another alias <code>title</code>.</p>
  
  <p>I am running the following query:</p>
  
  <pre><code>$sql = 'SELECT
          CASE WHEN session.title IS NOT NULL
             THEN session.title
             ELSE course.title
          END AS eventTitle,
          CONCAT(eventTitle, "\n", session.city, ", ", session.state) AS title,
          FROM session
          LEFT JOIN course ON course.id = session.course_id';
  </code></pre>
  
  <p>I get the following error:</p>
  
  <blockquote>
    <p>Unknown column 'eventTitle' in 'field list'</p>
  </blockquote>