drupal7 : db_select node with multiple values field
I've often struggled with the join methods in the D7 database layer. When I've needed to use a join, I've just used db_query() and passed it my SQL string. I know that when calling the join() method, you must already have the object initialised. So:

$query = db_select('node', 'n');
$query-&gt;join(field_data_field_date_programme_culturel', 'fdfdpc', 'fdfdpc.entity_id = n.nid');


and you already have it like this so I don't think that's the issue. I'd suggest using db_query($sql).