title: Prestashop - I get error when I use $this->_select in adminController
body: <p>When I extends adminController, and define attributes to display in  $this->_select variable, Prestashop display this error: </p>
  
  <blockquote>
    <p>You have an error in your SQL syntax; check the manual that
    corresponds to your MySQL server version for the right syntax to use
    near ' a.store_name, a.id_product FROM <code>ps_selstock_product</code> a ' at
    line 3</p>
  
  <pre><code>      SELECT SQL_CALC_FOUND_ROWS
                    , 
      a.store_name,
      a.id_product          FROM `ps_selstock_product` a
  
  
                    WHERE 1 
  
                    ORDER BY a.`id_selstock_product` ASC LIMIT 0,50
  </code></pre>
  </blockquote>
  
  <p>My $this->_select variable contains: </p>
  
  <pre><code>$this-&gt;_select = '
          a.store_name,
          a.id_product';
  </code></pre>
  
  <p>I know the query should be like this one, deleting ',':</p>
  
  <pre><code>SELECT SQL_CALC_FOUND_ROWS
  
      a.store_name,
      a.id_product          FROM `ps_selstock_product` a
  
  
                    WHERE 1 
  
                    ORDER BY a.`id_selstock_product` ASC LIMIT 0,50
  </code></pre>
  
  <p>But I don't know how to process because the query is built by prestashop I defined just the attributes to display</p>