title: Postgresql - concat_ws like function?
body: <p>I'm having a first painful experience with postgresql, and the minute-challenge of the moment is :</p>
  
  <p>How to perform a <a href="http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_concat-ws" rel="noreferrer">concat_ws</a> in postgresql, to join several fields value from a group by :</p>
  
  <pre><code>select concat_ws(';',field_lambda) from table_lambda group by id;
  </code></pre>