[Andreas]

You can use the variables $hook_query_fields to add new fields, $hook_query_joins to add joins and $hook_query_where to add conditions.

Example

PHP Code:

$hook_query_fields .= ", mytable.foobar1, mytable.foobar2";
$hook_query_joins .= " JOIN " . TABLE_PREFIX . "mytable ON (mytable.userid=user.userid)";