DQL provides the keyword IN for checking direct membership of a component in a virtual document. Suppose that the virtual document in the book example has the object ID 0900006480002533. The following query retrieves information about all the chapters and the virtual document itself:
SELECT r_object_id, object_name
FROM dm_sysobject
IN DOCUMENT ID('0900006480002533')
WITH ANY r_version_label = 'CURRENT'
If all the descendants in the hierarchy are desired, the keyword DESCEND can be used after ID().
Further, suppose that books are being represented as a custom type book_doc and stored somewhere in the folder tree under a cabinet named books. The following query retrieves the names of all such books:
SELECT object_name
FROM book_doc
WHERE r_is_virtual_doc = 1
AND FOLDER('/books', DESCEND)