Hi,
In the #__cck_core table, the 'id' column contains the id of the cck content and the 'pk' column the id of the Joomla object, in your case, the id of the Joomla! article linked to the cck content.
If you need to create a link on frontend to your content, it has to point to the Joomla! article id and not the cck id. The article will be loaded and Seblod will do the magic to load your fields.
Olivier