title: get the previous row of a query
body: <p>Doing a select I get a row, and I would want to get the previous row in the table. </p>
  
  <pre><code>create table t1
  id char(3),
  dat datetime
  ); 
  
  id        dat
  a  2014-04-21
  b  2014-10-01
  c  2014-10-15
  
  select id from t1 where id='c'
  </code></pre>
  
  <p>and wanted to find the previous row i.e. <code>b</code></p>