title: COALESCE or CASE more efficient and/or standard
body: <p>In terms of x compared to y.  </p>
  
  <ul>
  <li>Does x comply with sql standards better? [apologies if subjective]  </li>
  <li>Is x more efficient than y?</li>
  <li>Or are these scripts completely different and to be used in different contexts?</li>
  </ul>
  
  <p>x</p>
  
  <pre><code>    SELECT * 
      FROM   a 
             INNER JOIN b ON
             COALESCE(b.columntojoin, b.alternatecolumn) = a.columntojoin
  </code></pre>
  
  <p>y</p>
  
  <pre><code>    SELECT * 
      FROM   a 
             INNER JOIN b ON
             (case when b.columntojoin is null then b.alternatecolumn else b.columntojoin end) = a.columntojoin
  </code></pre>