title: MySQL Return the first non-NULL value from the list of the column in select statement with column name
body: <p>I have a sql query below:</p>
  
  <pre><code>SELECT 
      md.refereeInternetSearch,
      md.refereeCompanyColleague,
      md.refereeIndustryPeer,
      md.refereeIndustryEvent,
      md.refereeIndustryPublication,
      md.refereeMarketingEmail,
      md.refereeOther
  FROM
      marketing_details md
  WHERE
      md.id = 14588
  </code></pre>
  
  <p>From the 7 columns in the above select statement only one column will have a value and rest will be null. Is it possible to select just that one column value that is not null using some sort of sql statement ? </p>